The Digger  

He spawns in the room where the Relic of Sholoth is. There are two tunnels that give access to this area. One is at the back of the guards in the Sentry Stone of Sholoth's room. The other tunnel is in that room, but you have to climb to enter.
I got him to spawn from "a worshipper of decay" that roams the first tomb on the left, as you get out from the second tunnel. I guess there is at least another ph, which should also be "a worshipper of decay". Those may be in the middle of the area, in between the tombs and the first tunnel entrance.

He has around 6.8 million hp and casts several spells
1. Dollop of Filth http://everquest.allakhazam.com/db/spell.html?spell=31132
2. Immunity Suppression http://everquest.allakhazam.com/db/spell.html?spell=31133
3. Cloud of Decay http://everquest.allakhazam.com/db/spell.html?spell=31223 This triggers Strike of Decay
4. Strike of Decay http://everquest.allakhazam.com/db/spell.html?spell=31224

Was able to 3 box him with only T4 VOA gear on all toons