Your posture becomes stooped forward, and you grow a muzzle complete with fangs. You gain one bite attack each round, instead of or in addition to any other attacks you have, that deals 1d8 points of damage (assuming you are a Medium creature) when it hits.
Your bite attack is a natural weapon, so you are considered armed when attacking with it, and it can be affected by powers, spells, and effects that enhance or improve natural weapons. You can choose to deal nonlethal damage with your bite, taking the standard -4 penalty on your attack roll. If you bite as your only attack, you use your highest base attack bonus on the attack roll, and you can apply your full Strength bonus to damage. If you bite in addition to making other attacks, the bite is a secondary attack.
If you are not a Medium creature, your bite attack's base damage varies as follows: Fine 1d2, Diminutive 1d3, Tiny 1d4, Small 1d6, Large 2d6, Huge 2d8, Gargantuan 4d6, Colossal 6d6.
Based on your psychic warrior level, your bite increases in ferocity as noted here: at 5th level your bite deals an extra 1d8 points of damage, at 10th level an extra 2d8, at 15th level an extra 3d8, and at 20th level an extra 4d8 points.