Magic has so many merfolk that I probably missed a good one or two
2 Black Suns Twilight Probably the most powerful member of the Suns Twilight cycle, the black entry is a fairly-costed instant speed removal spell that can also create a huge value swing in Midrange matchups
Cycling ( , Discard this card: Draw a card.) Cid, Timeless Artificer Rarity: Uncommon TYPE: Legendary Creature SUBTYPE: Human Artificer CMC: 4 Mana cost: USD: $2.78 EUR: 3.57 TIX: 0.17 EDHREC RANK: 12038 (4/4) Artifact creatures and Heroes you control get +1/+1 for each Artificer you control and each Artificer card in your graveyard
The coven mechanic and abilities like Sigardian Zealots are great ways of gating the power of spells and abilities, which is healthier for the format in the long run
Note that some of these effects may function correctly only if it is a creature, and will not do anything productive since the copy is an artifact, not a creature
In horror, theyre always making people make hard choices, where there is no winning