msem-instigator

Whenever you attack, each opponent loses 3 life unless they discard a card or sacrifice a nonland permanent. Repeat this process once.
Fleeting {B}{R} (You may cast this spell for its fleeting cost. If you do, sacrifice it at the beginning of the next end step.)

Whenever you activate a nonmana ability of a permanent during your turn, you may choose one that hasn't been chosen yet this turn —
• That permanent becomes a 3/3 Dragon creature with flying in addition to its other types until end of turn.
• Each opponent discards a card and loses 2 life.
• Copy that ability. You may choose new targets for the copy.

Flying, trample
Whenever Skali, the Last Sunfeather attacks, abound. If a creature spell is cast this way, you may have that creature enter tapped and attacking. (To abound, you may cast a spell that costs less than this from your hand without paying its mana cost.)

When Skelephant enters, you may mill three cards.
Foresight — Whenever you draw your second card each turn, you may put target creature card from your graveyard on top of your library.

Resolute — Skerry Serpent must be blocked if able as long as its power is greater than its base power.

Target creature gets -1/-1 until end of turn, a second target creature gets -2/-2 until end of turn, and a third target creature gets -3/-3 until end of turn.

Flying
Spells you cast from anywhere other than your hand cost {2} less to cast.
Spells your opponents cast from anywhere other than their hand cost {2} more to cast.

This spell can't be countered.
{U}: Exile Skulkling. Return it to the battlefield under its owner's control at the beginning of the next end step.
{1}{U}: Until end of turn, Skulkling gets +1/-1 and can't be blocked.
{3}{U}: Draw a card. Create a 1/1 blue Rogue creature token.

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

Creatures can't attack you unless their controller pays {2} for each of those creatures.
Whenever a permanent is returned to a player's hand, create a 1/1 white and blue Bird creature token with flying.

Flying
When Sky-Torrent Navigator enters, forebode. If you control two or more Pirates, forebode again. (To forebode, create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.”)

Flying
Cycling {U} ({U}, Discard this card: Draw a card.)

Flying
Tap two untapped creatures you control: Skymount Commander gains double strike until end of turn.

Trample

Advance {5}{B}{B} (Cast this for {5}{B}{B} to advance it as it enters. {5}{B}{B}: Advance this as a sorcery.)
Whenever Sluiceway Collector advances, put a permanent card from a graveyard onto the battlefield under your control.

When Slyten Analyst enters, you may search your library for a card, then shuffle and put that card on top. If you do, you lose 2 life.

Smelting Breath deals 5 damage to target creature. Destroy up to one Equipment attached to that creature.

Flash
Wither (This deals damage to creatures in the form of -1/-1 counters.)

Up to two target creatures can't be blocked this turn. Until end of turn, whenever either of those creatures deals combat damage to a player or planeswalker, you draw a card.

Snowy Misthorn can block creatures with distorted as though it was tapped.

Flying, vigilance
Whenever one or more other creatures you control attack, those creatures get +0/+2 until end of turn.
Whenever one or more other creatures you control block, those creatures get +2/+0 until end of turn.

Whenever Solemn Stag perseveres, put two +1/+1 counters on it. (A creature perseveres when it survives damage.)

Create a 4/4 red Dragon creature token with flying.
Showcase {5}{U}{R} (Then if you cast this for its showcase cost, create a 1/1 red Bard creature token that can't block and exile this. Whenever it attacks, you may cast a free copy of this.)

Creatures you control get +2/+2 and gain trample until end of turn.

Alpha (You may have this creature enter with a +1/+1 counter on it. If you do, it becomes alpha and can only attack alone.)
Whenever a creature you control attacks alone, untap all lands you control.