Gez said:
Eaten ones may moan and groan, but do not speak or otherwise attempt to communicate.
The Aura of Hopelessness radiates the effects of an 8th-level spell to all characters with a 60 foot radius (i.e. just about everyone), and the 20 DC is very high for 5th-level characters (and for that matter, I'm not sure how the 20 DC came about, since 10 + HD + Cha. mod. = 16). On top of all that, it's a nonmagical Extraordinary ability, which seems inappropriate if not impossible to justify (e.g. the ooze secretes a fume that acts as a depresent).
The Acidic Corpse ability is also a bit heavy-handed for a 5th-level group, many of whom will lack sufficient spellcasting firepower to take it out from a distance. The party members that don't succumb to hopelessness (if any) will likely wind up assaulting it with weapons, which will take 2d6 acid damage each time they hit it and quite likely leave them weaponless even if they manage to destroy the eaten one.
Personally, I'd tone down the aura to sane levels, giving it the appropriate saving throw of 16 and making it a gaze attack, and allow a creature striking the Eaten one a Reflex save to avoid the acid damage.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.