The ability will not improve to the next level until it reaches 100%. Abilities may only be improved once every 24 hours, unless purchased with Favor Points.
Fangs: Buy 100 - Improve 20% for 1,000
Better Fangs: Buy 500 - Improve 20% for 2,000
Greater Fangs: Buy 1,000 - Improve 20% for 4,000
Superior Fangs: Buy 2,000 - (can't improve)
Vampire Claws: Buy 700 - Improve 20% for 7,000
Better Vampire Claws: Buy 3,500 - Improve 20% for 14,000
Greater Vampire Claws: Buy 7,000 - Improve 20% for 28,000
Superior Vampire Claws: Buy 14,000 - (can't improve)
Read more at Suite101: Vampire Wars Improving Offensive Abilties Guide: Improve Vampire Wars Offensive Abilities for higher Attack / Defense