Genius Loci, roughly translated, means "local spirit". This makes spotting one very difficult because it can take the form of anything in it's surroundings. It can appear as a field, a stone, or a grove of trees. The Genius Loci itself has no intelligence, but rather emulates the characteristics of its currently enslaved creature.
Colossal Ooze
Initiative: -2 (Dex)
Speed: 5ft./burrow 5ft.
Armor class: 0 (-2 Dex, -8 size)
Attacks: 10 slams +64 melee
Damage: Slam 4d10 +20
Space/Reach: Varies
Special attacks: Enslave, improved grab, constrict 4d10 +30
Special qualities: Blindsight 200ft., fast healing 50, ooze traits
Saves: Fort =43, Ref +21, Will +30
Abilities: Str 50, Dex 6, Con 50, Int ---, Wis 24, Cha 26