In Magic: The Gathering, an early-round mana boost can be game-changing, and Mana Vault is one of the most cost-effective ways to achieve this, especially if it's played alongside cards with an untap effect
This could also see play in +1/+1 themed Commander decks
Im giving it a whirl simply due to the fact that it replaces itself
Qala can actually get huge fast, like these cards often can, after which it can threaten a serious board pump for your attackers
This set brings all sorts of famous and retro land cards back into the TCG, and sure enough, it's a very old, very valuable land that I'm talking about today: Ancient Tomb
All of these, as well as similar instants, take Kalamax infinite (or to some arbitrarily high level of power and toughness) by having Kalamaxs copy of your Fork effect copy the original, then having that new copy do the same, then repeating ad nauseum