mtg card vault Mana edition set contains fifteen transforming Magic Mana Vault | MTG Cards

The Ur-Dragon

This can find you the perfect card to play in the next turn, or set you up for a combo with Conspicuous Snoop

Gravebreaker Lamia is the perfect example of this: not only do you search your library and put that card into your graveyard, but she makes it so that spells you cast from your graveyard are cheaper

Krasis was always a great late-game, top-end way to refuel your hand and push into the late lategame, but it's miserable early on

Traveling Chocobo would be great just with the doubling effect, but it comes with the added bonus of being able to play lands and cast Bird spells from the top of your library