Herigast is a neat Emerge build-around for mono red
Its technically three abilities, which are 1) You may cast the half of this card that has Aftermath from the graveyard, 2) You may ONLY cast the half of this card that has Aftermath from the graveyard, and 3) if this spell was cast from the graveyard, exile it if it would leave the stack for any reason
Blowing up one nonblack creature, then immediately blowing up another without expending any mana keeps our mana pool fresh so we can continue to flashback more and more destruction from our graveyard
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I enjoy when protection spells can serve multiple purposes like this, so I even made a mono-white Humans deck this year specifically so Id have an excuse to play this card (and Roaming Throne)
During the Beginning phase, players ready their cards, any effects in play that begin at the start of a turn take effect, and players draw a card from their deck