We might borrow some inspiration from this...
Amoebic Crawler
Large Ooze (Extraplanar)
Hit Dice: 4d10+32 (54 hp)
Initiative: +0
Speed: 30 ft. (6 squares)
Armor Class: 9 (-1 size), touch 9, flat-footed 9
Base Attack/Grapple: +3/+7
Attack: Tentacle +2 melee (1d6 plus 1d6 acid)
Full Attack: 2 tentacles +2 melee (1d6 plus 1d6 acid)
Space/Reach: 10 ft./10 ft.
Special Attacks: Acid, improved grab, vile touch
Special Qualities: Blindsight 60 ft., immunity to electricity, ooze traits, translucent
Saves: Fort +9, Ref +1, Will -4
Abilities: Str 10, Dex 11, Con 26, Int -, Wis 1, Cha 11
Skills: -
Feats: -
Environment: Any
Organization: Solitary
Challenge Rating: 3
Treasure: Standard
Alignment: Always neutral
Advancement: 5-12 HD (Large); 13-24 HD (Huge)
Level Adjustment: -
Acid (Ex): An amoebic crawler's acid does not harm metal or stone.
Improved Grab (Ex): To use this ability, an amoebic crawler must hit with its tentacle attack. It can then attempt to start a grapple as a free action without provoking an attack of opportunity. If it wins the grapple check, it establishes a hold and deals damage automatically every round (those grappled are affected by its vile touch ability).
Translucent (Ex): Amoebic crawlers are hard to see, even under ideal conditions, and it takes a DC 10 Spot check to notice one. Creatures who fail to notice a crawler and walk into it automatically take acid damage.
Vile Touch (Su): Those grappled by the slimy tentacles of this creature sometimes glimpse images from the Far Realm, and the sight sends them into screaming, explosive convulsions of nausea. Each round a creature remains grapple, it must succeed on a DC 12 Will save or be nauseated for that round.