Goblin Riot Starter

Haste
When Goblin Riot Starter enters the battlefield, you may pay {x}. If you do, reveal the top X cards
of your library. For each Goblin card revealed this way, flip a coin. For each heads, cast a Goblin card revealed this way without paying its mana cost. For each tails, put a Goblin card
revealed this way into your graveyard. Shuffle the rest of the revealed cards into your library.