You need to get to him with about a half hour to spare. Then, when engaged, other named pop in the dungeon (or mayube slightly before engage, been too long to remember). While those other named are up, he heals himself from their lifeforce. You need to send people to the other named and take them out. Once they are gone, you can damage this one until he dies.
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Pain Mistress Okami L`Assundre of Tarew Marr Dark Elf Shadow Knight Drinal (Tarew) Retired after 500 days /played Deleted http://eqplayers.station.sony.com/character_profile.vm?characterId=455266869792 Remade http://www.magelo.com/eq_view_profile.html?num=96950 Retired again