Rengar

Rengar, the Pridestalker is an upcoming champion in League of Legends.

Abilities
Rengar's abilities don't have a cost related to them and their use is only limited by cooldowns. Instead he uses Ferocity as his secondary bar.

Rengar builds 1 point of ferocity with each ability he uses on enemies (including structures and neutral monsters). Upon reaching 5 ferocity Rengar gains the ability to cast an alternate set of abilities, which are empowered versions of his basic abilities. The two ability-sets do not share cooldowns, and his basic abilities will continue to count down while his empowered abilities are available. His empowered abilities have no cooldown, and can be used as frequently as 5 ferocity becomes available.

The bonuses of his skills and their empowered counterparts stack. For example, Savagery followed by Empowered Savagery will grant up to 150% attack speed.