Custom Game Mode Idea: LockDown
Inspired from the Relic from Risk Of Rain, LockDown would, every minute, make you unable to use a random ability. The entire game, you will always be down one ability and it is up to you and your team on how to work around it.
Playing Annie and Tibbers go locked down? Better play safe for a bit.
Playing against a Yasou and you see he isn't using his q's? Better take advantage.
This gamemode would involve timing your ability's lockdowns, and your enemy's lockdowns to win fights.
(Oh and then there is
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