As part of the eventThe Hunt Is On!, Rengar and Kha'Zix are assigned to defeat one another in battle. The first to score a kill on the other claims victory (assists count). The event begins randomly after Kha'Zix has used all 3 evolution points, Rengar is in possession of the Bonetooth Necklace with at least 10 stacks, and all members of both teams must be alive for the event to start.
If Kha'Zix is victorious, he gains a fourth evolution point.
If Rengar is victorious, his Bonetooth Necklace is replaced with the Head of Kha'Zix, which grants him the bonuses of a fully stacked Bonetooth Necklace.
This event can only occur once per game, even if both teams possess both champions. A video describing the event can be found here.
Unique Active - Sweeping Lens: Summons a drone at the target location for 4 / 6 / 10 seconds (400 / 600 range). The drone reveals and disables all invisible traps and wards within an 400 / 600 unit radius. (90 second cooldown). At 20 Trophies, you also gain true sight for 8 seconds.
Unique Active - Scrying Orb: Reveals small location within 2500 / 3500 / 4000 range for 1 second (120 second cooldown). Enemy champions hit will be revealed for 5 seconds. This does not affect stealth champions.
Unique Active - Soul Anchor: Consumes a charge to instantly revive you at your summoner platform and grants 125% movement speed that decays over 12 seconds. Soul Anchor starts with 1 charge, and gains additional charges at levels 9 and 14. (Max: 2 charges).