From the Depths

Islandwalk
Whenever a player draws a card, instead that
player shuffles their library, splits it into two
face down piles, reveals the top card of each of
those piles, and makes an opponent of their
choice play those cards without paying their
mana cost. Those two piles are treated as
separate libraries.
If there is more than one library under a player's control, that player applies any and all effects
towards one library to all of them.