Rengar's abilities have no cost related to them and their use is only limited by cooldowns. Instead he uses Ferocity as his secondary resource.
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. Using an empowered ability consumes all 5 Ferocity. The two ability-sets do not share cooldowns, and his basic ability cooldowns will continue to count down while his empowered abilities are available. His empowered abilities have no cooldown and can be used any time 5 Ferocity is available.
Unseen Predator
Range: 600
While in brush or stealthed, 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.
If Rengar has a Bonetooth Necklace with 9 or more trophies, the leap range is increased to 750.
Savagery
Cooldown: 8 / 7.5 / 7 / 6.5 / 6
Active: Rengar's next basic attack deals bonus physical damage and grants him increased attack speed for 4 seconds.
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: Rengar lets out a battle roar, dealing magic damage to nearby enemies. If an enemy is hit by Battle Roar, Rengar also gains bonus armor and magic resist for 3 seconds.
Active: Battle Roar also heals Rengar for 40 + (20 × level) health, regardless of whether the ability hits an enemy. Basic and Empowered Battle Roar's defense bonuses do not stack with each other.
Bola Strike
Range: 575
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 snares 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 0.75s 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.
6300 or 
975
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