an amorphous mass  

The common drop of this mob is: Pliable Goo.

https://everquest.allakhazam.com/db/item.html?item=5059

There are actually only two goos in DN that I am aware of, both not far from each other and both in the Paebela (good rats) cave. Both goos have the same name.

The first one is in the tunnel leading from the pool with the entropy serpent to where the hole is where you drop down into the chetari pool with vilefang, etc. This goo wonders down that tunnel, is light blue to me at lvl 61, and pretty easy. He does not split into any more goos when dead. He is also KOS to all. This goo dropped "pliable goo" which has 1 charge of regeneration.

The second goo is closer to Neb. When you follow the underwater tunnel past the pool you go left instead of right (right goes to Neb). This goo does not wander but is larger. He cons dark blue at lvl 61 and cons indifferent. He only attacks when hailed. This one is much more difficult, he must be mid to high 50's. I did not kill him so don't know if he splits, but got him close to dead. He summons AND enrages, and stuns. Max hit only 137 but hits fast.

this lvl thing saying 49-51 is real wrong. they conned red to me at 52 and beat the **** outa my grp as well *tho that could be that the cleric was standing on an aoe trap :/* and they seemed a great deal larger when we were fightin em than the picture too...course i'm a dorf...
The great and powerfull Wolveseax
< 52 war bertoxx- lost boys >

some of these goos will aggro if you go near them but some will only aggro if you hail them

These start out as a large goo, bigger than the ones in HS or CoM. Upon their death, they will split in to 1-4 new masses. Large ones split, small ones (pictured here) are the last stage, kill em and they die permanently.

They are completely unmezzable, though not magic resistant.

The can drop a number of different "goos" All one charge items with effects from regeneration, all the way to Resusitation (39 rez) as well as quest gems.

Pulling a single mass can eventually end up with 10+ masses killed as you work through the splits. Slow em, and have a tank keep them occupied until your group is ready to finish it.