msem-instigator

Flying
Suisei the Southern Star gets +1/+1 for each comet counter you have.
Whenever you cast an instant or sorcery spell with mana value greater than the number of comet counters you have, you may pay {R}. If you do, return Suisei from your graveyard to the battlefield, then you get a comet counter.

Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)
Whenever Sullivan's Heralds or another creature you control becomes renowned, add mana equal to the number of +1/+1 counters on it in any combination of {R} and/or {G}. Until end of turn, you don't lose this mana as steps and phases end.

Pay 2 life, Sacrifice a Clue: Draw a card.

Vigilance
Sun's Own has indestructible as long as it's your turn.

Whenever you gain life for the first time each turn, draw a card.
{3}{G}{W}: You gain life equal to the greatest toughness among creatures you control.

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

Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{3}{R}{W}: Creatures you control gain flying and haste until end of turn.

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.

Pressure {3}{B}{G} (You may cast this spell for its pressure cost if seven or more cards are in your graveyard.)
When Sunken-Eye Angler enters, mill three cards. Then if it was cast for its pressure cost, you may return a creature card from your graveyard to the battlefield.

Flying, haste
Assault {1}{R} (Whenever this attacks, if it has no +1/+1 counters on it, you may pay its assault cost to put a +1/+1 counter on it.)
Whenever one or more +1/+1 counters are put on a creature you control, you may return Sunnula's Firebird from your graveyard to your hand.

Sunwing has flying as long as it's your turn.

Whenever Supplanter of Realities attacks, proliferate. (You choose any number of permanents and/or players with counters on them, then give each another kind of a counter already there.)
Sacrifice another permanent: Supplanter of Realities gains indestructible until end of turn. Tap it.

Haste
Ward—Pay 3 life.
Whenever Surface Expeditioneer attacks, if it's embattled, it deals 2 damage to target player or planeswalker. (A creature is embattled if it has a counter on it or a permanent you control attached to it.)

Whenever a creature you control becomes the target of a spell, that creature gets +3/+3 until end of turn.

Flash
When Surreal Bakhtak enters, choose one —
• Destroy target tapped creature.
• Tap up to three target creatures.

Flying, prowess
Whenever Surveyor of Skies attacks, you may return a permanent you control to its owner's hand.

Each other Rogue creature you control enters with an additional +1/+1 counter on it.
Remove a +1/+1 counter from a creature you control: That creature can't be blocked this turn.

Whenever Swift-Fingered Sneak enters or attacks, you may discard a card. If you do, draw a card.

First strike
Whenever Ren deals combat damage to a player, you may activate one of her abilities by paying 3 life rather than paying its cost.
{1}{R}, Discard a card: Draw a card.
{2}{B}, Sacrifice a creature: Each opponent sacrifices a creature.

Flying, first strike
When Swiftclaw Griffin enters, return a creature you control to its owner's hand.

Whenever Swiftspear Ambusher and exactly one other creature attack, put a +1/+1 counter on target attacking creature.

Swiftstep Cliffdweller has haste as long as you control another Goblin.

Flying
When Swooping Razorbeak enters, you may return another permanent you control to its owner's hand.

First strike
When Sworn Cohort dies, you may search your library for a legendary card, reveal it, put it into your hand, then shuffle.

Vigilance
Whenever a legendary creature you control enters, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)