Yuan Ti Abomination
HD: d8

Level 1: +2 Str, +2 Int, +2 Wis, Climb/Swim speed 20, Bite 1d6, Darkvision 60ft
Level 2: +2 Con, +2 Cha, Natural Armor 2, Constrict 1d6, poison, scent, Produce Acid 1d6
Level 3: +2 Str, +2 Int, +2 Wis, Bite 1d10, Aversion, Detect poison, Chameleon 
Level 4: +2 Con, +2 Cha, Natural Armor 4, Improved Grab, Animal Trance, Entangle (at will), Produce Acid 2d6
Level 5: +2 Str, +2 Int, +2 Wis, Large Size (reach), Bite 2d6, Deeper darkness, Neutralize Poison, Suggestion (3/day)
Level 6: +2 Con, +2 Cha, +2 Dex, Natural Armor 8, Baleful Polymorph (1/day), Produce Acid 3d6
Level 7: +2 Str, 2 Int, +2 Wis, Natural armor 10, Alternate Form.