msem-instigator

First strike
Whenever Martial Maestro attacks, other attacking creatures you control get +1/+0 until end of turn.

Target creature you control fights target creature you don't control. (Each deals damage equal to its power to the other.)

Stalwart Guardian has first strike as long as it's attacking.
Augmented — When Stalwart Guardian enters, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, create two 1/1 blue Elemental creature tokens with flying.

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

Return target card from your graveyard to your hand.
{1}{G}, Tap an untapped Shaman you control, Exile Whisper of the Wild from your graveyard: Return target card from your graveyard to your hand.

Enchant creature
Enchanted creature gets -3/-0.
Spells that target enchanted creature cost {1} more to cast.

Submerge up to two target attacking nontoken creatures an opponent controls. (To submerge a card, exile it, then put it on the battlefield face down under its owner's control as a 2/2 creature.)

Kicker {U} (You may pay an additional {U} as you cast this spell.)
Flying
If Aven Ranger was kicked, it enters with a +1/+1 counter on it.

Double strike
Creatures you control have trample.
Excess noncombat damage that would be dealt by sources you control to permanents an opponent controls is dealt to that player instead.

Trample
Tribute 3 (As this creature enters, an opponent of your choice may put three +1/+1 counters on it.)
When Rockpounding Saurian enters, if tribute wasn't paid, you may destroy up to one target artifact, up to one target land and up to one target Fortress.

When this creature enters, look at target opponent's hand. You may exile a nonland card from it. For as long as that card remains exiled, its owner may play it. A spell cast this way costs {2} more to cast.
Arise {2}{W}{W} ({2}{W}{W}, Exile this from your graveyard as a sorcery: Create a black token copy of it that's also a Zombie and can't block.)

Lionize {2}{R} ({2}{R}, Exile this card from your hand: Put a +1/+1 counter on target creature and it gains the following abilities until end of turn. You may cast this card on a later turn from exile.)
Double strike

(Transform this if it's not attached to a creature. Pay {3}{U} as a sorcery to unattach it.)
Enchant creature you control
Gamhaugen Warbeast's rider gets +2/+2 and has flying.

Whenever you cast a spell with mana value greater than Script Jockey's power, put a +1/+1 counter on Script Jockey.

Menace (This creature can't be blocked except by two or more creatures.)

Trial 3 (As you cast this spell, an opponent of your choice may pay 3 life. If they don't, they fail the trial.)
When Glimmering Prosecutor enters, if the trial was failed, create two 1/1 black Devil creature tokens.

GenTech Labs enters tapped.
{T}: Add {G} or {U}.
{G}{U}, {T}: Create a Function token with “This spell costs {1} less to cast if its mana value is 5 or greater.” Activate only if you have four or more cards in hand. (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

At the beginning of your end step, you may put a progress counter on Sparkline Harness.
[progress 1-3] Whenever an artifact creature you control attacks, it deals 1 damage to target opponent.
[progress 4+] Whenever a creature you control attacks, it deals 1 damage to target opponent.
Whenever a creature you control attacks, it deals 1 damage to target opponent.

When Rousing Battlehound enters, other creatures you control get +1/+1 until end of turn. Other Hounds you control gain first strike until end of turn.

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.)

At the beginning of your upkeep, each player discards a card.
Whenever Waking Watcher attacks, if defending player has no cards in hand, it gets +3/+3 and gains menace until end of turn.

Choose target creature you control, then choose two —
• Put a +1/+1 counter on it.
• It gains hexproof until end of turn.
• It can't be blocked this turn.

When target creature you control dies this turn, return it or another creature card with an equal or lesser mana value from your graveyard to the battlefield tapped.

Counter target spell. If that spell is countered this way, draw a card, then discard a card.

Gain control of target creature until end of turn. Untap that creature. It gains haste until end of turn. Create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)