Characters have abilities which strengthen themselves and different from enhancing which increase characters' stats. Abilities are used for enhancing same title characters and not for being used in a battle.
How to acquire abilities
By being enhanced with using a same title character as a material, the character can get abilities. However, acquiring abilities often fail to be done successfully.
Types of abilities
The effect of abilities varies from increasing stats, such as Attack Boost and Health Boost, to supporting characters in a battle, like Combination Critical Rate Boost and Reduce Skill Damage.