Just a quick guide from memory to give some info I was looking for myself earlier now that I've figured it out.
Where to go:
The new Shavarath area is another plane, so you need a expert in planar traval to take you there. The guys at the twelve have that. Head to the Twelve, into the tower. First door straight ahead. The NPC inside will take you to Amrath, the new public instance with quest NPCs, Vendors, etc.
What it has:
4 new very long Yugoloth Favor Quests - which are are also the new raid prereqs:
Bastion of Power
A New Invasion
Sins of Attrition
2 short side quests - Twelve Favor:
Wrath of Flame
12 man Raid - The Tower of Despair
How to flag for the raid:
Very easy, run the 4 long yugoloth quests (short ones not required). After that a new NPC will show a ! over his head near the others, and offer you the "Devil you know" Quest.
How to get to the raid:
From the Devil Battlefield, head towards Genesis Point, but go past it. Loop around and mostly hug left always going up towards the huge tower of despair. There is a map on the wiki you can check out. Once you are there, you can talk to a NPC to get a convient quick teleport option, to Amrath and back to the raid. So do this as a 6man group first before you do the raid. Map here:
How to become immune to the Banishment: Craft the Boots of Anchoring (see below) (you wil want for your melee in the Tower of Despair Raid, and perhaps all classes as a backup. and/or get the Mantle.
For healers/casters I strongly recommend the Mantle of the Worldshaper) as it will serve the same function as the boots in any decent group, but also is more powerful in that it will prevent you from being stunned during the banishment. Also this item is much easier to acquire then the boots as it's a 100% gaurenteed end reward from a low lvl chain that takes only 30-90 minuits to run. Note it only handles 5 banishs and mistakes like getting too close ot the bosses may waste charges, so having the boots as a backup as well isn't a bad idea, tho personally I'd make them all on my melee's first. Mantles don't work as well for melee as Horoths meteor swarm and Suulomades chain lightning tends to drain it fast.
How to craft the boots of anchoring:
Find 4 ingredients from the new quest, they are as follows:
Demon Blood - Bastion of Power - Either End Chest (not bonus End Chest)
Mysterious Artifact - Weapons Shipment - End Chest (not optional) or A New Invasion - Locked Prisoners Chest or End Chest
Pure Shavarath Iron - Weapons Shipment - End Chest (not optional) or Genesis Point - End Chest (Any option)
Devils Keepsake - Weapons Shipment - End Chest (not optional) or Sins of Attrition - Any End Chest
All the items are low drop rates, but do not bind so you can trade them.
Once you have all 4 items. Bring them to the Planar Traval NPC that will offer you send you out of Amrath. Select the bottom option to ask about the boots of anchoring, then give her the ingredients and she will make you a set. Be sure the 4 ingredients are in your main backpack, not your ingredients bag. The Boots do bind and have no other stats then Anchoring - which makes you immune to haste, and banishment. Level18+ to wear.
Some quick tips for each quest on how to prepare for them and what to take: (Some spoilers here)
From easier to hardest (in my opinion)
Bastion of Power:
Pretty straight forward hack and slash quest. Be sure to have some melee DPS and basic healing.. Nothing too hard. No really class recommendations other then some melee, any should work well. Only major difficulty can be the dungeon alert bug - so try to move slowly and kill everything to avoid as much as possible.
It has allot of portals that monsters come out of - you can kill them.. But thats entirely optional with no bonus for doing so.
Decent challenge fight against a Horned Devil who can cast reverse gravity. Has several trash mobs which respawn fairly fast. You can either beat him down quickly, or go for a more complicated approach to get a bonus chest:
As you get his hitpoints down, he will cast reverse gravity at 75%/50%/25% of hp marks.. You should have some people in the room below the red banners, to try to get up to the platforms above to light 3 runes. Once the third rune is light, the boss will die instantly and the chest will be available after the quest is complete. Be sure to jump down after lightning the runes - killing the portals has no real effect.
After the Horned Devil is dead, the Demons attack you. This is a moderately difficult fight as the Marilith can hit very hard.. However she attacks very infrequently and can be DPS'd down very fast on normal difficulties (requires some more intense teamwork and strategy on elite). Melee, Firewall or Blader barriers all work fine, just ignore her trash mobs and beat her down quickly. If your group has a caster, hitting the trash mobs with flesh to stone can be a great idea to make the fight easier. Also note the spell: gust of wind will make quick work of the enemies otto's sphere of dancing, which can lead to an untimely death if left untended.
It seems the longer the fight goes on the more quickly the enemy demons will respawn, so killing her fast will most often ensure the easiest victory.
A bit more complicated quest, but most encounters aren't much more difficult then
Bastion of Power.
Step 1 - Levers.
How to do the levers:
Start out going straight at the first fork.
Hit every portal lever (spikey ones in the fire pits)
Also note the 2 spikey ones on the adjacent wall facing the lower level - these will toggle the doors below.. However some are 1 time use, so do not hit them all at random. Look at the doors below, and only hit them if the door is closed - you want all the doors open.
Buttons/Valves: Most rooms buttons/valves aren't important (most just control the fireball launcher) - except the south room. The west room just control the canons - you hit all the outside buttons to arm them, then the central button (looks different) to fire. All it does is break crates and the mobs fight each other sometimes, doesn't help much. The north room controls the prisons.
Levers with red runes near the in sets of 3: Don't seem to serve any purpose. They will open the doors you can see across from the upper area - leading to another central area.. But far as I Know no one has learned how to access that area yet? Perhaps bugged.
After you completed a full circle of the area, hitting all portal levers - a shrine and portal will spawn. Use the shrine imediately as you should still have the one at the start for a backup. Then head north again, and use the portal you see.
The other levers on the walls, in sets of 3 don't seem to do anything.. I hit em anyways so not sure if they have any effect yet. There 1 time use and won't hurt anyways far as I know tho.
Defeat the Army. Straight forward, run over to the army area and slaughter them.
Free the Prisoners. To do this hit the lever on every fire prison.. Then send half of your team to go up and hit the set of 5 valves, they unlock the prisons accordingly. Keep in mind some orthons will be around so better to spilt into 2 teams, not have 1 person go solo.
Have 1 team head to the maze area past the area where you fought the amry, and another back up to the south side of the top floor to do the levers. The order is simple: Have the ground go clockwise around the bottom to reach the upper left entrance to the maze. Levers: First hit the lever once, so it's facing down - this will disable the traps in the maze.
Next hit the third valve, going from left to right - this opens the first door, have the maze team go thru. Next hit the first valve - this open the door to the center. Done.
Soon as everyone reaches the center - the vial on the ground is the key to continueing to the end of the quest. Using it will trigger a full party teleport to a mini-boss fight - so be ready. It doesn't matter if your groups all spilt up, everyone will go regardless of where they are.
Warning: Do not touch the light. It's bad.
Step 4.5 (optional) - go get the chests you missed in the maze, there are 2.
Select a Portal Lever to pick 1 of 4 quest endings:
West = Beat down the portals, similar to shroud. Not particularly difficult but can be quite long without a lot of melee dps.
North = Free the Archon Prisoners. Fairly difficulty, more challenging then the portals due to some more tricky spilt team work required and some respawns (more levers and prisoners to free) tho the boss isn't too bad.
East = Defeat the Devils Leader. Possibly the shortest route and if you kill everything, highest exp route (onslaught bonus available vs other route which only give aggresion unless you kill respawns for hours), but a tough boss.
South = Defeat the Mephits. Requires some splitting up and teamwork. The mephits them self are quite easy, but needs some careful teamwork to get it done.
A New Invasion:
One of the more challenging quests due to the end fight. Recommend you take a caster for the quest itself due to many air elementals flying around, best to insta kill those (actually since the air elemental nerf it barely matters, tho a caster will still speed up this quest). Otherwise most any group can work, just some standard melee dps is needed, nothing that tough. Quest is mostly straight forward - run around 3 semi random levels finding either a hole or a portal to go down 1 level, and a boss fight at the end. At the 2nd level you'll find many prisoners behind locked doors, freeing all of them will result in allot of exp, so if you have a rogue and move quickly it can be wortwhile. Most doors can be easily knocked, but some are harder and may require lockpicking or a extremely high knock DC.
Recommended way to do in a pug is use a smaller group. If you have a full group of 6 people, it's actually easier to have some stay up above. Just take 1-3 people maximum. Generally 1 melee + 1 cleric works well, tho 2 melee or 2 clerics can work if all are fast and can stay close together.
The hard part about this is the traps.
How they work:
6 tiles, with 6 time-delayed traps. The center is permanently traped. The traps work on a simple time delay. The moment anyone touchs a tile - a trap will charge up, it takes about 3 seconds for it to appear, and will go off within 3 more seconds, so you can only remain on 1 tile for 5 seconds at a time. Else this happens: 18 second curse called soul drain - makes you immune to healing, can be removed by remove curse. Also the trap deals 20-40 untuped damage - no save, and may hit multiple times at once (up to 10+ times sometimes, dealing 200+ damage)
My Basic Strategy:
Drop down fully buffed, no featherfall so you get down at the same time (ramps will modify FF speed causing poor timing)
Melee gets pit fiend agro, moves down to a tile. Cleric stay very close by on the same time. Try to kill trash while holding aggro. Fight ~2-4 seconds on 1 tile, then move clockwise to the next tile in unison. Never stay still for long of the trap will hit you. Continue to move and dps and it should be good as long as you do not get hit by the trap.
Alternative method such as a ranged dps kiting or even casters with blade barrier/polar ray/acid fog/ball lightning will work too. But will generally take much longer then melee.
Sins of Attrition:
Very tough quest for pugs and newer players due to the trash mob setup. The end boss itself can be extremely easy compared to other quests (depending on the item you select and if you do the optional) - and can be made even easier by "discovering the weakness" objective (depending on the item you select - you have to do a different optional room to discover the weakness)
What's hard is that almost every encounter involves 5-15 devils at once, requiring some very heavy CC/Healing/DPS to live thru each one without deaths. Take appropriate resources for that. There is really no easy way to avoid them or pull them apart as they are statues that only trigger once someone runs up, and will teleport over to attack all other party members (actually there is one way - intimidate wil disable there teleport ability for 6 seconds, should you have someone with sufficient skill) - even at the very start of the quest! (some more advanced and complicated tactics like using invis/stealth can limit the encounter size, but this is rarely nessasary in a group)
Recommended Party Setup:
One very high HP tank with good DPS
One very tough dedicated healer (cleric, favored soul or bard) who can take a hit (or 10 hits)
One Rogue (has many traps which hurt, but can be avoided if you can't find a rogue)
One Bard to enhance the groups DPS with buffs like haste, displacement and rage, and perhaps offer some CC like ottos irresistable dance. A healer bard can filll this role too, or even a good arcane.
2 others perhaps, tho going with 4 should be fine due to scaling tech on normal.
It also has several random chests, seems to be 3, which are random regardless of what item was selected.
What the items cause:
Which optional you can complete and which end fight you get will vary depending on what item you select.
Gula's Ham (Meat) -Gluttonous Orthon Fighter end boss (very easy)
Tome of Inferal Knowledge (Book) - Tiefling Wizard end boss (easy)
Iwra's Ritual Ingredient's (Vial) - Gnoll Sorcerer end boss (very easy with optional, moderate without)
Offering to Avaritia (Gold) - Bearded Devil Warrior end boss (moderate)
Badge of Cenodoxus (Crest) - Horned Devil Barbarian end boss (moderate with optional, hard without)
Acedia's Lute (Guitar) - Troglodyte Bard end boss (easy with optional, moderate without)
Note on optionals: Pretty much all the optionals involve you simply killing a few monsters and handing in the item. For each of these, if there is a random chest (not dependant on what you selected) it will unlocked after you complete the opitonal.. Except 1:
The Badge/Bearded Devil optional (first side area on the left) He has several dialog options... Oddly succeeding on most of them will result in him surrendering and then teleporting away, and the chest will remained locked. The only way to get the chest is to fail his intimidate check and then kill him.. So always go for the killing route. I think regardless of what you do here, the end boss will be weakened. Note if you don't have the crest and the chest is there, you simply cannot get the chest. Thus the only way to ensure you get 100% chests every run is to take the badge and thus risk running into a slightly tougher boss then the others.
The Tower of Despair Guide (Heavy Spoilers):
Overall this is a pretty straighforward hack and slash raid. Just requires some melee DPS and lots of healing to get through. Really only requirement party wise is melee DPS and some strong healing - tho even scroll healing can get you through the entire raid.
Run up and hit the lever to start it up. Doing so will close a gate behind your party and open one to continue.. So at this point be sure your entire raid group is in and ready to go. You can buff during the intro cutscene to save time.
Recommended buffs: Mass Deathward (Judge Enervates), Anything to increase saves (prayer, stalwart pact, etc) (lots of fireballs and lightning bolts). Resists: Fire (lava), Sonic (orthons) Lightning (Judge), Acid (Tiefling arrows). Not much cold damage.
Phase 1 - The Judge and The Jailer:
Basic notes on them:
Jailer - Orthon:
DR10/Good (Fairly minor so using your best DPS weapons is usually fine) But on hard/elite scales much higher so be sure to bypass it.
No trueseeing ability, so use displacement on the tank
Judge - Horned Devil
DR15/Good + Silver (Be sure to bring appropriate weaponry for him)
Has trueseeing like all horned devils, dispalcement won't help
Inflicts a healing curse on critical hits.. Using a warforged tank is a good idea. Else remove curse, or break enchant to remove multipel curses at once.
The objective is to kill both, but it's best to take 1 at a time. The Jailer is easier so generally kill him first as theres less risk of anyone being lost in the fight, while the Judge is either kited around or shield blocked. Recommend Fighting in the northwest corner out of the lava - as it does some decent damage since the latest patch, and the buffets aren't as often so regrouping after a buffet isn't too hard. Healers should stay down as well, otherwise a boss may teleport over to them and if there up top - it takes too long for the melee to reach them to help.
The main tank should keep his back to the wall so he gets buffeted into the south wall (where there are no spikes).. This lets him get back down and re-astablish agro faster, other on the back may get shot off far buts there's no priority for them to get back like the tank.
Assign at least 3 people to kill the fire elementals - these do not respawn and can deal some heavy damage to your party so elimnate them ASAP. The hell hounds do respawn, but slowly, so assign 1 or 2 people to take care of them (can be flesh'd to stone or just killed)
Once the Jailer goes down, apply the same strategy to the judge. Keep him facing the wall so only the tank gets the curse/damage.
Phase 2 - The Shadowmaster and his Fiends:
This can often be the hardest part of the raid and it requires some strategy to beat. How it works: The Shadowmaster sits as his throne - and should be fought there. He himself isn't very hard, but has a fair amount of hitpoints making it a long fight. About 6 seconds after he activates, his shadowfiends come out to slaughter the party - and if they get close, you will be slaughtered. They deal 180-300 cold damage, it's an aura effect that will hit everyone around soon as they get close - they need not attack you, soon as they are close you will get hit.
Basic Notes on the Shadowmaster:
DR15/Good + Silver, higher on hard/elite. Standard pitfiend abilities: Poisons/Disease attacks. Casts meteor swarm and horrid wilting. Has a permanent Ice shield effect. Buff approprirately (Fire, Ice resistance all around). Overall not a particularly tough boss, but still enough of a challenge to require most of your group up there and un-headed by the fiends.
So the objective is to keep them off the main DPS group fighting the shadowmaster. This can be done by a single person - but it's safer to have a backup incase he goes down. This party member should A: Self heal decently, Run fast - haste is enough to pull it off - they run at the exact same speed as a hasted character, but Barbarian/Monk speed can be helpful to keep them outpaced, and have a reliable ranged attack to get agro fast (The Shadowfiends have about 41AC, so +40 attack ranged attack works well - my 20 dex Barbarian had this with bard buffs at lvl20) Also Firewall is very effective for picking up the agro, as it's guarenteed no save damage.
At first 2 shadowfiends come out of the 2 doors nearest to the shadowmaster. A caster can place firewalls near the steps leading to the throne to prevent any from reach the party, or anyone with ranged can stay back and throw/shoot at them as they come. Kite these 2 around the pillars for a while, and eventually they will disapear - but it's not safe yet. Soon after, the 6 blue barriers in the room will lower, giving the shadowfiends more ways to get into the room. 2 more will apear together, then 1 more every ~10 seconds, which will come out of a random doorway, tho generally the one closest to the party. There doesn't seem to be a limit on them, at once time I successfully kited 14 of them at once.
Pick them all up and keep them off the party long enough to take down the boss to ensure victory.
Phase 3 - General Horoth and his righthand Suulomades
This is a pretty simple straight up tank and spank fight. With a couple tricks thrown in to mix it up. Really depends heavily on your tank and healers. A high hitpoint tank will be the most reliable here, as a lower-hp AC tank will still take significant damage due to the no-resist damage over time effects he applies to you, and the 500+ point disintegrates he likes to cast. A tank with over 600 HP has a chance to survive them even if he rolls a 1, while a lower HP, AC oriented tank does not. Luckily they are quite rare and not a high DC, so for a good tank only a roll of 1 will cause the heavy damage. But really either will high AC or high HP tanks will work well, the most important thing is that they hold the agro well. The cleric capstone - Divine Intervention can help allot here, as even if your tank gets disintegrated, he will live and Horoth will not gain a big heal. Agro will still be lost unfortunately (it allows you to get incapped), so having a backup tank is a good idea.
Basic notes on the 2 bosses:
Attacks with melee and spells. Does standard pitfiend things (poison and disease) on attacks. Casts meteor swarm and greater shout often. Sometimes powerword stun and sunburst. Have a tank with appropriate defensese and buffs (resist fire lightning sonic and good saves buffs like circle against evil, prayer and/or recitation) In additional to his heavy melee and spell damage, he can apply up to 3 100% unresistable damage over time debuffs. They can't be removed in anywayas so you just need to heal through the damage. One of only does a small amount of damage, but if you get hit by at lall 3 youll need rather heavy healing.. So no matter how good your tanks saves/dr/hp/ac/etc is, he will need some amount of healing.
Does quite a bit less melee damage then horoth but is still a serious threat for a few reasons: Casts fairly powerful chain lightning, hitting everyone nearby. On critical hits (can be quite often) he inflicts a healing curse, this prevents any type of positive energy healing, but not repair/reconstruct. As such a warforged tank and arcane with recostruct spell to keep him going works quite well.
Defenses of both bosses:
High saves. Evasion on elite. DR15/Good + Silver on normal, DR scales up to as much as 25-35 on hard/elite. Bring appropriate weapons.
Horoth can banish you back to ebberon. (Note: if you get banished, you may still come back in for completion credit and end-reward, but can't get the chests) It has a willsave of about 30 on normal. You don't want this to happen to your melee's, so make sure that at least most of them have the boots of anchoring before you start the raid. Casters/Healers and anyone who will be staying far enough back can rely on the Mantle of the Worldshaper, as it's a superior item for the first 5 banishs (absorbs both the stun and banish, 1 charge per)
However the boots make you immune to haste, lowering your DPS.
However you can fix this: Horoths Banishment is easy to identify and he seems to have at least a 1 minuit cooldown on casting it.. So you are safe to take your boots off imediately after a banish attempt to get a haste.
How to identify it: It looks like horrid wilting but a bit more purply, and is called Blasphemy. It will always be cast only on the person with agro, but it is a massive AOE - that covers nearly the full length of the room (but not quite). The stun portion has a smaller AOE, about the maximum standard healing length.. So healers will generally be stunned, but anyone doing ranged DPS from a long distance is safe from it, but anyone melee'ing or healing generally is not.
You may see this text over your head or in your combat log. And in addition to the banish, it's also a AOE stun (no save on the stun portion) - so if you suddenly see someone stunned - you know it just happened, and they either saved against the banish or had boots on. You can still get stunned with boots on,as it is a seperate save roll.
If anyone dies, Horoth heals immensely, about 20-25% per death.. Do not die.
3 portals will spawn, about 20 seconds apart.. Each will have 2 orthons that come out of them, and they will respawn every 30 seconds after dieing. They aren't too much of a threat, but will interfer with your efforts if not taken care of. They have the crucible of shavarath, so you can't vorpal or instakill them, however they are not red named.. So casters may take them out fast with a quick energy drain + flesh to stone. However these orthons serve the tower at all cost, and will suicide after 1-2 minuits of being stoned, then respawn. So flesh to stone is still effective for stopping them for a bit, but not 100% reliable. Ideally assign at least 2 people to take care of them, 2 casters works well, or 1 caster + 1 melee.
Portals: The portals can be killed, but will respawn rather fast and not slow down the orthon spawn. So there is little purpose to do so.
Suulomades: Once Horoth reach's about 60%, Suulomades will jump down to aid him. He is quite a tough boss and takes a large effort to kill him - he has about as many hitpoints as Horoth - however he is optional and thus sometimes not worth killing if your group does not quite have the power to do so. So having 1 good tank kite him around or shield block while the rest of the group focuses on Horoth works. He will teleport away once horoth dies.
It is possible to get 2nd chest depending on if you kill suulomades or not in the last part. Killing him will gaurenteed a bonus chest. This chest may drop +4 tomes as of the latest update, so it's well worth it.
Strategy on killing suulomades:
Suulomades influcts a curse that prevents healing everytime he scores a critical hit, and thats often as his threat seems fairly high (and there's no way to prevent it other then shield blocking) so having a warforged tank with a arcane reconstructing him can make this much easier. I recommend pulling him off to the right between the thrones, theres an area you can stick him where he will not turn, thus all the DPS can swithc off horoth and get on him. Take him down asap then head back to horoth.
Kraldor (Devils Keepsake info)
Spyderwolf (Bastion of Power bonus chest info)