I don't quite understand why does Rengar's ult get cancelled by activating the item. I mean yomumu doesn't cancel his ult, why does edge of night? If you want to make use of it on Rengo you have to use it and hope you get to jump on them before the shield expires :/ 
Krell3561 votesBecause Edge of night counts as a channel. Maybe Riot will add an exception for it in the future?
EDIT: Also Rengar can already mess up people just fine with his ult without also having an on demand spell shield. He would be vastly overpowered if it did work.
Rito Staff1 votesIt's kind of better the way it is if you think about it, forces Rengo to act quickly. I dunno, I have nothing against him so far but the idea of changing your course of action due to having Edge of Night seems neat.
JustMonika131 votesEoN active spell shield is a channel; while you may still move, it doesn't stop being a channel. AAing, activating an ability, and/or getting CCed while channeling will interrupt it.
Youmuu's is not a channel. It is an instantaneous effect.
