unfinity mtg commander deck The Must-Have Cards For MTG Unfinity un-set cards will

You get bonus points for using instant-speed discard outlets on your opponents turns to buff their attacking creatures

Does not include the card

Or two big cards, who knows

It makes your opponent put a card from their hand on top of their library, so you can create a soft lock where your opponent just draws the same card every single turn

At the end of each of your turns you can choose to have one opponent lose life equal to the life that they lost that turn, or you can gain life equal to the life you've gained that turn

Fomori Vault isnt very flashy for a mythic rare, but its an extremely handy effect for an aggro deck to have in your back pocket (or on an untapped land, which is basically the same thing)