hypnotism (3rd), delay poison (5th), summon monster III (reptiles only) (7th), poison (9th), hold monster (11th), mass suggestion (13th), summon monster VII (reptiles only) (15th), irresistible dance (17th), dominate monster (19th).
Combat Casting, Combat Reflexes, Deceitful, Deft Hands, Persuasive, Silent Spell, Skill Focus (Bluff), Stealthy.
Your powers of compulsion can affect even bestial creatures. Whenever you cast a mind-affecting or language-dependent spell, it affects animals, magical beasts, and monstrous humanoids as if they were humanoids who understood your language.
The treacherous and yet hypnotic serpent's blood that flows through you taints your magic with a sinuous and seductive grace.
Serpent's Fang (Ex)
At 1st level, you can grow fangs as a free action. These fangs are treated as a natural weapon inflicting 1d4 points of damage plus your Strength modifier (1d3 if you are Small) plus poison (Bite—injury; save Fort DC 10 + 1/2 your sorcerer level + your Constitution modifier; frequency 1/round for 6 rounds; effect 1 Con damage; cure 1 save). At 5th level, these fangs are considered magical for the purpose of overcoming DR and the poison damage increases to 1d2 Con. At 7th level, your poison requires 2 successful saves to cure. At 11th level, your poison damage increases to 1d4 Con. You can use your fangs for a number of rounds per day equal to 3 + your Charisma modifier.
At 3rd level, you can use speak with animals at will with reptilian animals (including various forms of dinosaurs, lizards, and other cold-blooded creatures), and you gain a viper familiar using your sorcerer level -2 as your effective wizard level.
At 9th level, you gain a +1 bonus to natural armor, a +2 racial bonus on saves against poison, and a +2 bonus on Escape Artist checks. At 13th level and 17th level, these bonuses increase by +1.
Den of Vipers (Sp)
At 15th level, you may summon a host of writhing serpents. This power acts as creeping doom, but the swarms' poison inflicts Con damage and any creature other than you sharing a space with a swarm is entangled. You may use this ability once per day.
Scaled Soul (Su)
At 20th level, you gain the shapechanger subtype, and you can assume the form of a reptilian humanoid (as alter self) or snake of Diminutive to Huge size (as beast shape III) at will. You retain the power of speech and the ability to use somatic spell components when transformed. You also become immune to poison and paralysis. You may use serpent's fang as often as desired, and you may choose to inflict damage to any ability score.