Almost forgot to ask about the crystal,too silly me.
The naga transformation gives some stat bonuses like the other transformations. It gives you a bite that injects the same venom the Cobra uses and a more powerful version of the Grapple attack that constricts the enemy. You can use the constrict on the Kobold to get an item that will increase your muscle based on the enemy's fat.
The White Crystal increases the amount of arousal you gain each turn in battle