Preparation There are multiple ways to get to this mob. I am going to list the path that takes you through no CPK until you get to the mob.
Also note that these areas are no-form, so as such you will be unformed. When I did this, Psychosis was enabled in keep which makes this significantly easier as you can all join in on the fight against the mob with only one person "tanking".
This mob is in the soundproof area of keep, which is west side. Take the third west north of southwest corner of keep. Follow path w, sw, s. Then go Down (non-visible room exit). He's down here. TBC.
*Please note: This area is toggleable and can, at times, be NPK or CPK.
Encounter The zombie Trex hits for a decent amount of damage, but is definitely able to be solo'd if you so desire. He has a seemingly random emote that will insta-kill you by biting your head off. Seems to be no rhyme or reason to when this happens and can happen to anyone in combat with him (possibly just in the room?). Other than that, he has no special combat routines, just dispel, spell up with as much as possible and grind it out.
You can flee sw of him to flee into a NPK room to heal up as opposed to other rooms which are CPK.
Loot Generic boss loot
You sense the following: The zombie Tyrannosaurus is a 28 year old, level 500 Skeleton, and is aligned to Death, the Releaser of Life and Ender of All Things. The zombie Tyrannosaurus is immune to: summon charm steal petrification paralysis The zombie Tyrannosaurus is resistant to: magic pierce slash The zombie Tyrannosaurus is vulnerable to: negative mental necromantic The zombie Tyrannosaurus has a Saving against Spells and Most Spell Effects modifier of 14. The zombie Tyrannosaurus has a Saving against Paralysis (i.e., Sleep, Web, Slow, etc.) modifier of 100. The zombie Tyrannosaurus has a Saving against Petrification (i.e., Abjure, Kill, etc.) modifier of 100.Plus Sanc/haste.