A Warlock, for those who don't know, is an arcane caster who gets his or her power by making a 'pact' with a chaotic or evil outerplanar entity, usually in return for some service. What the warlock gains is literally infinite power; basically, he or she is a spellcaster who doesn't use spell points. The flipside to this is that, out of all the spellcasting classes, the warlock has the fewest spell slots. That is, 4 per invocation (the term for a warlock's spells) level. Note that a first level (least) invocation is either a first or second level spell for the purposes of calculating DCs, while a fourth level (dark) invocation is equivalent to a seventh or eighth level spell.
Chaotic or Evil Outerplanar Entities/Factions:
- Rakshasa/Demons (Khyber)
- Devils (Shavarath)
- Daelkyr (Xoriat)
- Eladrin (they're *chaotic* good, after all)
Some other stats about warlocks:
- d6 HP class, 2 + int modifier skill points per level
- Light armor and simple weapon proficiencies, but no shields.
- 3/4 BAB per level
- No ASF in light armor, all spells/invocations use Charisma for the DC (usually, depending on the pact).
- Class Skills: Bluff, Intimidate, Spellcraft, UMD, Concentration.
- Required Alignment: Any evil OR any chaotic. (In DDO this would mean that they're restricted to CG and CN)
Also, they gain the ability to regenerate hit points over time using a feat called "Fiendish Resilience", and gain DR/ Cold Iron over class levels, along with resistances to two different elements as they level up.
The main ability of the Warlock, however, is the Eldritch Blast, which is a single-target force damage spell that increases in damage as the warlock goes up in levels, like any other invocation, this can be used infinitely, and the damage increases at the same rate at rogue sneak attack damage dice does. As the warlock levels up, the Eldritch Blast can also be shaped into a melee attack, ray spell, cone, chain or circular AoE by taking the appropriate invocations, and can also be made into acid, fire or ice spells that deal the same amount of damage as the Eldritch Blast.