My idea was :

The new items are Ruby's
You can gain 1 Ruby by playing 10 Multiplayer Battles
For 50 Ruby's you can open an Ruby Chest
The Ruby Chest contains :
30 % Mythical
60 % Legendary
10 % Epic

In this way people Will want to play more to get the Chest so they get an reward for playing a lot.

so the real fans get an reward for playing and the other people dont

Thanks for listening.

I dunno... this chest is a little too good for my liking. don't get me wrong, it's a great idea to have a battle-to-earn idea, but maybe try it to be a win-to-earn and make the legendary and epic chance a little more even.

finally a good idea in this section

*cheering and clapping* give yourself a pat on the back!