Size & Type: Medium Undead
Space/Reach: 5'/5' (Tentacles have 10' Reach)
HD: 8
Speed: 30'
Ability Scores: Str +8, Dex +4, Con -, Int +2, Wis +4, Cha +2 - Net +20, no penalties
Natural Armor: 6
Natural Weapons: Two Primary "Tentacle Bites" (2d4)
Skill List: Escape Artist, Hide, Listen, Move Silently, Spot
Body Shape: Humanoid
Speech (Languages): Not Specified. Has a mouth and intelligence.
CR: 7
WotC LA: -
Our LA: -0
DR 10/magic which might possibly still be relevant for a bit, Spell Resistance 20 which definitely is, +4 Turn Resistance, and Improved Grab on its tentacles with no listed size limitation (which sadly means it defaults to smaller creatures). A decent chassis to start with.
In addition to IG, the Gunthosh can use Blood Drain every round it grapples something, dealing 1d4 Con Drain.
Finally, as a standard action it can lob a negative energy-infused Spittle of Darkness up to 30' away. With a ranged touch attack, the Gunthosh can inflict 1d4 negaive levels and blind the target until someone takes a full-round action to clean it off. These negative levels never result in actual level loss, but that will hopefully be irrelevant.