Infinity War
Right, before we start if this isn't possible due to copyright. Then @#$%. 
But anyway,
I got thinking the other day after watching a tonne of Avengers Infinity War trailers and here's the idea that came out of that thought process:
Infinity War Event on LoL.
So essentially, near the release of Infinity War (the movie) an event would start. Each of the 6 infinity stones would be given to a champ:
Mind Stone - Unknown at the time being (give any ideas of who you think) Time Stone - Ekko Reality Stone - Leblanc Power Stone - A Sol Space Stone - Ryze? Maybe? Soul Stone - Yorick?
(These are all just ideas of the holders)
When any of these champs is on your team you're playing for an infinity stone. If you win that game, you 'get the infinity stone'. So if you have an Ekko on your team and you win, you 'get the Time Stone'. Once you 'have' all 6 of the stones, you 'get a gauntlet' and maybe an emote/ the profile pic thingy. Then you try to get all 6 stones again. Once you have the gauntlet and the 6 stones you get a gift of some sort.
Here's the catch, if you currently 'have' a time stone and you lose to a team with an Ekko on it, you lose the time stone. And if you have multiple of the stone holders on your team when you win, you choose only one of the stones you don't already have to take. Same thing if you lose to a team with multiple holders you choose which one you lose, if you have more than one. However you cannot lose the gauntlet. Once you have it, you have it.
Just an idea however your feedback is appreciated.
Yet again, if this is copyright territory, well @#$%. 
Time Stone
or
Reality Stone
Power Stone
,
,
or
Space Stone
,
, or
Soul Stone
,
, or 