I've played LoL long time ago and it had it, but haven't noticed it here.
If opposing teams got Rengar and Kha'zix, it will trigger a "final fight" at a certain level.
If Rengar first gets a kill/assist against Kha'zix - he receives a special trophy - Head of Kha'zix, which gave more stats or something.
If Kha'zix first gets a kill/assist against Rengar - he receives a 4th evolution point.
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