Pantlaza, Sun-Favored [The Lost Caverns of Ixalan Commander]

Whenever Pantlaza, Sun-Favored or another Dinosaur enters the battlefield under your control, you may discover X, where X is that creature's toughness. Do this only once each turn. (Exile cards from the top of your library until you exile a nonland card with that mana value or less. Cast it without paying its mana cost or put it into your hand. Put the rest on the bottom in a random order.)