Duel and achievements
Every 10 minutes the two strongest champions in the entire game are selected to fight a duel in a pit which is isolated from everyone else to prevent interference from other individuals in the game (1v1) the winner of this duel claims x amount of gold for his team and a buff for himself, this can then tie in to another concept that I have thought of which is not ingame but out of the game which are* achievements* say if you won 5 duels in a certain time period eg 1 month you get a reward either a certain amount of IP, skin or champion based on difficulty and rarity of achievement.
For one achievement such as earning a ribbon of that type x amount of times you get the ribbon name champion skin on one champion of your choice.