This was my first attempt at a Necro 2 mission, done at level 9 on a caster druid, solo with wolf along for company (no hireling), normal difficulty, gear is randomly found stuff. I'm still using the devotion Korthos set, to convey how good my druid's gear currently is.
I went into the mission, got swarmed almost immediately while at the center dias after dropping down, and used up half my mana to stay upright. Miraculously, my druid's wolf also survived with a sliver of life, due to keeping spring's resurgence up at all times. I went to one corner, fought everything off, and then found what looked like a human in one of those "depressed" areas that has staircases leading down into them from both sides. He had what looked like a staff in his hands. After hitting him a few times, phase spiders and shadows and other incorporeal enemies arrived and clogged up the screen.
About 5 seconds later, my druid went from full hit points (about 190 hit points, more or less) to dead. I checked the combat log, but could not understand what it was that killed my druid. That makes preparing countermeasures a little more difficult.
My best guess is that keeping up death ward becomes a "tax" on my druid's mana supply that I pay for my wolf and druid, for at least this mission. Will that do it, or is there a less expensive remedy?