msem-instigator

You may put a creature or Revelation card from your hand onto the battlefield. Exile that permanent if it would leave the battlefield. If it's a Revelation, it enters as a Horror creature.
Coalesce {7}{U}{U} (You may cast this from your graveyard for {7}{U}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Exile up to one target activated ability, triggered ability, or nonland permanent.
Coalesce {5}{G}{W}{U} (You may cast this from your graveyard for {5}{G}{W}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)
End of All Things enters tapped.

Menace
Whenever Entrail Elemental deals combat damage to a player, you may cast target card from your graveyard this turn. If an instant or sorcery spell cast this way would be put into your graveyard, exile it instead. (You still pay its costs. Timing rules still apply.)

Flying
Herald of Oblivion enters with X -1/-1 counters on it, where X is your life total.

Reconstruct {4}{B}{B}{B} (You may cast this from your graveyard for its reconstruct cost reduced by the mana value of a permanent you sacrifice as you cast it this way. Then exile this.)
Destroy all creatures. If The Afterlife Takes Its Due was reconstructed, create an X/X black Zombie Horror creature token, where X is the number of creature cards that have been put into graveyards this turn.

When The Third Breach enters, discard your hand, then draw seven cards.
Creatures you control get +3/+3, have haste, and are Horrors in addition to their other types.
At the beginning of each end step, sacrifice each creature you control.

Flash
When Veilborn Meddler enters, counter target spell if its mana value is less than or equal to Veilborn Meddler's power.
Whenever you cast a spell during an opponent's turn, put a +1/+1 counter on Veilborn Meddler.

Target player mills two cards.
Draw a card.
Coalesce {6}{U} (You may cast this from your graveyard for {6}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Cast a copy of target creature or Revelation card in your graveyard without paying its mana cost. If a Revelation is cast this way, it enters as a Horror creature after it resolves.
Exile Wish to See.

Each player shuffles their hand and each non-Revelation card from their graveyard into their library, then draws seven cards. You may put any number of land cards from your hand onto the battlefield.
Coalesce {6}{G}{U}{U} (You may cast this from your graveyard for {6}{G}{U}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)