Whenever Deeproot Wayfinder deals combat damage to a player or battle, surveil 1, then you may return a land card from your graveyard to the battlefield tapped. (To surveil 1, look at the top card of your library. You may put that card into your graveyard.)
Her warning raced through the roots and rivers of Ixalan: prepare for war.
The land card you return from your graveyard, if any, isn’t a target of the ability. You choose that card as the ability is resolving, after you surveil 1. It can be a land card you just put into your graveyard or one that was already there.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.