mtg 1488 card Altanak, the Thrice-Called | Duskmourn: House of Horror | Standard untap up to five lands. I don't get why this

Pay four life and whatever nonblack creature that's posing a problem suddenly disappears

Illustrated by Uriah Voth Standard Not Legal Alchemy Not Legal Pioneer Not Legal Historic Not Legal Modern Not Legal Brawl Not Legal Legacy Legal Comp

As you can see in the top left, this card is named Walking Corpse and its mana cost is one generic mana and one black mana (often shortened to one and a black or one black)

You gain control of that creature if it regenerates this way

This helps give more availability to the player base, which I always encourage

Entering the battlefield untapped and acting as a Cabal Coffers for your gates, this land boosts the power level of any gate-based mana base by an order of magnitude