msem-instigator

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever you casting a noncreature spell causes an ability of a creature you control to trigger, that creature gains your choice of first strike, haste, menace, or trample until end of turn.

As long as it's your turn, Shell Merc has first strike and prowess.

Exile all nontoken creatures. For each creature exiled this way, return that card to the battlefield under a random player's control.

Flying, haste
Whenever Shimmering Dragon attacks, for each creature you control, create a tapped and attacking token that's a copy of that creature. Exile the tokens at the beginning of the end step.

As an additional cost to cast this spell, discard a card.
Choose two. You may choose the same mode more than once.
• Draw a card.
• Return target card with a cycling ability from your graveyard to your hand.

Shining Showstopper deals 5 damage to any target. Audition for red. (Create a 1/1 Construct Actor creature token, a Warrior Role giving 3/2 and trample, or a Wizard Role giving 2/2 and prowess. Roles replace older ones.)

Whenever you sacrifice a permanent, put a +1/+1 counter on Shipment Overseer.
Surpass {5}{R} ({5}{R}: Transform this creature. This costs {1} less to activate for each counter on it. Activate only as a sorcery.)

Shock deals 2 damage to any target.

Equipped creature gets +2/+0.
Equipped creature has first strike as long as it's attacking.
Equip {2}

Shock Blast deals X damage to target creature, where X is the number of instant and sorcery cards in your graveyard.

Shock and Awe deals 2 damage to target creature. Creatures can't block this turn.

Vanguard — Whenever a creature you control attacks alone, Shocking Ewe deals 2 damage to defending player.

{T}, Sacrifice an artifact: Add {R}{R}{R}.

Haste
Each creature with toughness greater than its power can't block.

Choose one —
• Shredding Blizzard deals 5 damage to target creature.
• Up to three target creatures can't block this turn.

Haste
Whenever you sacrifice another permanent, put a +1/+1 counter on Shrine Razer.

When Siamang Minstrel enters, you may put a lore counter on target Saga you control.

Improve {1}{R} ({1}{R}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
When Siegebreaker Ogre enters, create two 1/1 red Goblin creature tokens with haste.

When Sihari's Groundblazer enters, create a red Aura enchantment token named Searing Crags attached to target land. The token has enchant land, “Enchanted land's name is Charred Causeway” and “Enchanted land has {T}: This land deals 1 damage to each opponent.”

Desecrate (When this creature enters, you may sacrifice an artifact or land.)
When Siltsplitter desecrates a permanent, each opponent sacrifices an artifact.

Menace
Whenever Silver-Dawn Radiant becomes the target of a spell or ability you don't control, it deals damage equal to its power to that spell or ability's controller.

First strike

Whenever Simian Striker attacks, it gets +3/+0 until end of turn.

Target creature gains trample and haste until end of turn. Harmonize. (Trigger up to one harmony of a permanent you control.)

Haste
At the beginning of combat on your turn, you may have target artifact or enchantment you control become a creature with base power and toughness X/X, where X is its mana value, in addition to its other types and gain haste until end of turn. (If it's attached to a permanent, it becomes unattached.)