Originally Posted by
procobrito
The Vault progress is one of the most important things in Arena, when you complet 100% you get 1 mythic, 2 rares, 3 uncommon wild cards, that you can change for any card of the dame rarity. Wild cards is what matters, since there isn't trade or dust, is the only gmway to you truly get the cards you want.
When you get the 5th copy of some card, you get an ridiculosly small increasment in your vault, instead of the card:
1.1% for mythic
0.7% for rares (I think)
0.3% for uncommons
0.1% for commons
You need to get 90 5th+ copies of mythic rares to trade the vault reward.