msem-instigator

{1}, Discard a card: Painted Watcher gets +1/+1 and becomes the color of your choice until end of turn.

Exile target creature you don't control. Its controller may search their library for a creature card with a different name, reveal it, put it into their hand, then shuffle.

As an additional cost to cast this spell, sacrifice a creature.
Look at the top X cards of your library, where X is the sacrificed creature's power. Put one of those cards into your hand and the rest into your graveyard.

Primal {1}{W}{W} (During your turn, you may cast this spell for {1}{W}{W} instead of playing a land.)
Return target creature card from your graveyard to the battlefield.

Whenever you gain life, target opponent loses that much life.

Destroy target token.

Creatures with power less than Skull-Crowned Chief's power can't block.

Target creature gets +2/+2 and gains lifelink until end of turn. Whenever that creature perseveres this turn, target opponent loses 2 life. (A creature perseveres when it survives damage.)

Whenever you cast a spell that doesn't share a color with Stinging Hunter, each opponent loses 1 life.

Primal {1}{G}{G} (During your turn, you may cast this spell for {1}{G}{G} instead of playing a land.)
When Swampedge Sentinel dies, return another creature card from your graveyard to your hand.

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

Starting with you, each player may sacrifice a creature. Each player that doesn't loses life equal to the total power of creatures sacrificed this way.

Sacrifice Voice of Ambition: Target creature gets +2/+1 until end of turn.

At the beginning of your upkeep, each player sacrifices a nonbasic land.

Creatures your opponents control have haste.

Whenever you cast a white spell, creatures you control get +1/+0 until end of turn.
Whenever you cast a blue spell, draw a card, then discard a card.

Target creature gets +X/+0 and gains trample until end of turn.

{1}{R}: Crashcaller Nereid gets +1/+0 and gains trample until end of turn.

Whenever Current Shaper perseveres, it deals 1 damage to each opponent. (A creature perseveres when it survives damage.)

Up to two target creatures can't block this turn.
Draw a card.

Primal {R} (During your turn, you may cast this spell for {R} instead of playing a land.)
When Deadeye Drowner enters the battlefield, it deals 2 damage to any target.

Whenever Deceitful Soul becomes blocked by one or more creatures, it gets +2/+0 until end of turn.

Damage dealt by Deepwater Stinger can't be prevented.

Flash
When Devious Naiad enters the battlefield, exchange control of it and target creature until end of turn. Untap that creature. It gains haste until end of turn.

Drown deals 2 damage to target creature. That creature can't block this turn.