Corpses of the Lost - The Lost Caverns of Ixalan

Skeletons you control get +1/+0 and have haste.

When this enchantment enters, create a 2/2 black Skeleton Pirate creature token.

At the beginning of your end step, if you descended this turn, you may pay 1 life. If you do, return this enchantment to its owner's hand. (You descended if a permanent card was put into your graveyard from anywhere.)