msem-instigator

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.

Striptide deals 1 damage to target creature. Unattach all artifacts from it. It becomes red until end of turn.
Draw a card.

{W}: Target creature gains vigilance until end of turn.

Heretic (Whenever you cast a spell that doesn't share a color with this creature, it gets +1/+1 until end of turn.)
{1}{W}: You gain life equal to Sunken Outcast's power.

Primal {1}{W}{W} (During your turn, you may cast this spell for {1}{W}{W} instead of playing a land.)
Double strike
When Sunken Slasher enters, if you didn't play a land this turn, put a +1/+1 counter on it.

Haste
Heretic (Whenever you cast a spell that doesn't share a color with this creature, it gets +1/+1 until end of turn.)

Thunder Wave deals 3 damage to target creature or planeswalker.

Undine Coven gets +1/+1 for each other Merfolk you control.
Whenever you cast a noncreature spell, Undine Coven deals 1 damage to target player or planeswalker.

Exile the top five cards of your library. Until end of turn, you may play any number of cards exiled this way with mana value less than or equal to the number of colors among permanents you controlled as you cast United Fervor.

Whenever Veiled Charmer attacks, target creature blocks it this turn if able.

Trample
Whenever a creature attacks, Alpha Stag gets +2/+2 until end of turn.

{T}: Add {G}.
{T}: Add {G}{G}. Activate only if you control an Elemental.

At the beginning of your first main phase, add an amount of {G} equal to Bloomhorn's power.

{1}{G}: Target land you control becomes a 3/3 green Elemental creature until end of turn.
{1}{U}: Target enchantment you control becomes a 2/2 blue Nymph creature with flying until end of turn.

Primal {G} (During your turn, you may cast this spell for {G} instead of playing a land.)
When Charging Nymph enters, it gets +2/+0 and gains haste until end of turn.

Whenever you cast a blue spell, you may cast creature spells this turn as though they had flash.
Whenever you cast a black spell, put up to one target card from your graveyard on top of your library.

Until end of turn, creatures you control gain “When this creature dies, return a noncreature card from your graveyard to your hand.”

Trample
Heretic (Whenever you cast a spell that doesn't share a color with this creature, it gets +1/+1 until end of turn.)

Target creature gets +3/+3 until end of turn.

{1}{U}, {T}: Reveal the top card of your library. If it doesn't share a color with Heretical Seer, put it into your hand.

For each color among nontoken permanents you control, add one mana of that color.