Flash

Trample

When Green Knight enters the battlefield, target opponent may choose to make a wager. If they do, you and that opponent each reveal the top card of your libraries. If your opponent reveals a creature card with higher converted mana cost, a creature they control gains double strike and indestructible until end of turn. If you reveal a creature card with higher converted mana cost, put your choice of a Vigilance or Indestructible counter on Green Knight.

Whenever the Green Knight deals combat damage to a player who lost a wager, you may search your library for a creature card with equal or lesser converted mana cost than the revealed card, put it onto the battlefield tapped, then shuffle your library.