msem-instigator

Each land doesn't untap during its controller's next untap step.

{T}: Envious Nereid deals 1 damage to target creature and 1 damage to that creature's controller.

Whenever an attacking creature dies, you may pay {R}. If you do, create a 2/1 red Merfolk creature token.

Whenever Impetuous Impetus deals combat damage to a player, you may sacrifice a land. If you do, Impetuous Impetus deals 3 damage to that player.

Creatures you control get +1/+0 for each color among permanents you control and have haste.
Whenever you cast a white, blue, black, or green instant or sorcery spell, copy it for each of its colors. You may choose new targets for the copies.

Destroy target artifact or land. If {U} was spent to cast Liquefaction, draw a card.

Target creature gets +3/+3 and gains haste until end of turn.

First strike

Haste
Whenever Nadei deals combat damage to a player, that player sacrifices a land. You may put a land card from a graveyard onto the battlefield under your control.

{T}, Discard a card: Draw a card.

Overkill deals 4 damage to any target that was dealt damage this turn.

As an additional cost to cast this spell, discard a card.
Draw two cards.

Whenever a noncreature permanent enters, Petaldiver deals 1 damage to that permanent's controller.

Whenever you cast a red spell, target creature gets +1/+0 and gains haste until end of turn.

Menace, haste

Whenever you cast a spell that doesn't share a color with Raloran Adept, you may switch target creature's power and toughness until end of turn.

Primal {R} (During your turn, you may cast this spell for {R} instead of playing a land.)
Target creature gets +4/+0 and gains trample until end of turn.

River's Wrath deals 2 damage to any target. If you've been dealt damage this turn, River's Wrath deals 4 damage instead.

Enchant creature
Enchanted creature gets +3/+0 and has menace.
Whenever enchanted creature deals combat damage to a player, discard a card, then draw a card.

If a player taps a nonbasic land for mana, that land produces {C} instead of any other type.
Whenever Rylei Wakebreaker attacks, it and another target creature you control each get +1/+0 until end of turn for each attacking creature you control.

Up to three target creatures each get +1/+1 until end of turn.

Whenever one or more nontoken Merfolk you control attack, create a 2/1 red Merfolk creature token.

{2}{W}, {T}: Target creature gets +2/+2 and gains first strike until end of turn.

Primal {3}{U}{U} (During your turn, you may cast this spell for {3}{U}{U} instead of playing a land.)
Draw a card for each land you control, then discard that many cards unless this spell was cast for its primal cost.

Heretic (Whenever you cast a spell that doesn't share a color with this creature, it gets +1/+1 until end of turn.)
When Shoring Naiad enters, if {U} was spent to cast it, you may return an instant or sorcery card from your graveyard to your hand.