Rengar's abilities have no cost related to them and their use is limited only by cooldowns. Instead, he uses his secondary resource bar to display his unique mechanic: Ferocity.
Rengar builds 1 point of Ferocity whenever he lands an ability. 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' cooldowns will continue to count down while his empowered abilities are available. His empowered abilities have no cooldown and can be used whenever 5 Ferocity is available, though using an empowered ability consumes all 5 Ferocity.
Range: 600 (750 with 9 stacks on Bonetooth Necklace)
While in brush or in stealth, Rengar gains bonus attack range and his attacks cause him to leap at his target. This bonus lasts for ~0.5 second upon exiting brush or stealth. This will happen regardless of whether or not his target has sight of him, and has no internal cooldown.
Cooldown: 8 / 7.5 / 7 / 6.5 / 6
Active: Rengar's next basic attack in the next 2 seconds deals bonus physical damage and grants him increased attack speed for 4 seconds.
Bonus Physical Damage: 30 / 60 / 90 / 120 / 150
Attack Speed: 30 / 35 / 40 / 45 / 50%
Cost: 5 Ferocity
Active: Savagery deals additional damage equal to 100% of Rengar's attack damage, and he gains increased attack speed equal to double the normal bonus. Basic and Empowered Savagery's attack speed bonuses can overlap and stack with each other.
Active: Battle Roar also heals Rengar for 20 + (10 × level) health, increased by 1% for every 1% of Rengar's missing health, regardless of whether the ability hits an enemy or not. Basic and Empowered Battle Roar's defense bonuses do not stack with each other.
Cooldown: 12 / 11 / 10 / 9 / 8
Active: Rengar throws a bola at his target, dealing physical damage and slowing it for 2.5 seconds. The slow decays over the duration.
Active: Bola Strike initially roots his target for 1 second. The slow is then applied in full after the 1 second, and decays over the remaining 1.5 seconds.
Thrill of the Hunt
Cooldown: 140 / 105 / 70
Active: Rengar activates his predatory instincts, stealthing himself after 1 second (delayed up to 3 seconds if taking damage) and revealing all enemy Champions in a large radius around him. He gains movement speed and generates 1 Ferocity per 0.75 second while stealthed. Lasts 7 seconds or until Rengar uses an ability.
If Rengar has a Bonetooth Necklace with 14 trophies, the duration is increased to 10 seconds. Additionally, Rengar's next ability used after activating Thrill of the Hunt generates 1 bonus Ferocity.