msem-instigator

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.)

Whenever Single-Minded Mob becomes untapped, it gets +2/+2 until end of turn.

[+1]: Gain control of up to one target noncreature permanent you don't control until end of turn. Untap it.
[0]: Target player gains control of target permanent you control.
[–7]: You get an emblem with “Whenever you target one or more permanents, gain control of those permanents.”

Double strike
Bushido 1 (Whenever this creature blocks or becomes blocked, it gets +1/+1 until end of turn.)
Whenever Sisters Suzakazi attacks, if you control another creature named Sisters Suzakazi, it deals 3 damage to any target.

Haste
Sixpod Sprinter can't be blocked except by creatures with flying or reach.

Advance {3}{R} (Cast this for {3}{R} to advance it as it enters. {3}{R}: Advance this as a sorcery.)
Whenever another artifact creature you control enters or a permanent you control advances, Skalorian Orbguard deals 1 damage to any target.

Haste
Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)
Legendary creatures you control have haste.

When Skeletal Shredwing enters, target creature can't block this turn.
Revive {5}{R} ({5}{R}, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

When Skhorvall Raider enters, if you control an embattled creature, Skhorvall Raider deals 2 damage to any target. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)

Menace
Whenever Skhorvall Warleader attacks, it gets +1/+0 until end of turn for each other attacking Warrior you control.

Whenever an opponent is dealt damage by one or more sources you control for the second time each turn, draw a card.

Skin from Bone deals damage to target creature equal to your fealty to Mountains. (Each Mountain you control counts towards your fealty to Mountains.)

Advance {3}{R}{R} (Cast this for {3}{R}{R} to advance it as it enters. {3}{R}{R}: Advance this as a sorcery.)
Flying, haste
Whenever Skiviar Scraplord advances, put a +1/+1 counter on it.

As an additional cost to cast this spell, discard a card and sacrifice a nonland permanent.
Draw three cards.