Crucias, Titan of the Waves

At the beginning of your end step, you may discard a card. If you do, create a Treasure token and choose ambitious or expedient. If you chose ambitious, seek a card with greater mana value than the discarded card. If you chose expedient, seek a card with lesser mana value than the discarded card.

Swamp

Mountain

Corrupted Conviction

As an additional cost to cast this spell, sacrifice a creature.
Draw two cards.

Caldera Breaker

Trample
When Caldera Breaker enters, exile all Mountain cards from your library. When you do, Caldera Breaker deals that much damage to target creature or planeswalker an opponent controls.
When Caldera Breaker dies, put all cards exiled with it onto the battlefield under their owner's control. Conjure four cards named Volcanic Geyser into your library, then shuffle.