The Fireball Ability is an upgraded version on the one time use Fireball. Unlike the normal Fireball, the Fireball Ability can be used many times, but with a cooldown. When used, it shoots a fireball that explodes on impact.
The Fireball Ability's item and description
Rarity: Rare
Cooldown: 20 seconds
Type: Combat
Chapter 2, Season 1: Added Fireball Ability.