msem-instigator

Menace
Whenever a creature blocks, put a -1/-1 counter on that creature at end of combat.
Creatures with -1/-1 counters on them can't block.

Menace
Whenever Algrin's Legacy becomes the target of a spell an opponent controls, that spell's controller loses 5 life unless they discard a card.

As long as you have more life than each opponent, prevent all combat damage that would be dealt to Alia, Bearer of Morning.
[+1]: You gain 4 life.
[–2]: Exile target tapped creature. Each player draws a card.
[–8]: You get an emblem with “{W}, Pay X life: Exile target creature with power X or less.”

[+1]: Create a 1/1 green Saproling creature token. You gain 2 life.
[0]: Creature spells you cast this turn can't be countered. As they enter, they gain hexproof until your next turn.
[–2]: Create a green enchantment token named Survival with “You and other permanents you control have ward {1}.”

Converge — Gain control of up to X target creatures with total mana value X or less, where X is the number of colors of mana spent to cast Alive and on Top.

Create two 2/1 black and red Cat Pirate creature tokens with menace. You lose 2 life.

If a creature would die this turn, exile it instead.
All-Consuming Fire deals 4 damage to each creature.

[+1]: Create a 1/1 blue Merfolk creature token with “When this creature dies, draw a card, then discard a card.”
[–1]: Target creature gets -2/-0 until your next upkeep and attacks during its controller's next turn if able.
[–7]: You get an emblem with “Creatures your opponents control get -4/-0 and attack each turn if able.”

This spell costs {1} less to cast for each artifact you control.
Draw two cards.

Flying, lifelink
Golden age (If you cast an instant or sorcery spell, activated a nonmana ability, and attacked this turn, enter a renaissance for this game.)
You may cast this card from your graveyard as long as you're in a renaissance.

Trample
Whenever a creature attacks, Alpha Stag gets +2/+2 until end of turn.

Double strike
Whenever an opponent casts a spell that targets you or a spell or permanent you control, Alrathan Outcast deals damage equal to twice its power to that player.
Alrathan Outcast gets +1/+1 for each Aura and Equipment you control.

Distorted (This creature can be blocked by tapped creatures but not untapped creatures.)
If a spell or ability would target you, it targets each player instead.
Whenever an opponent attacks you with one or more creatures, tap all noncreature permanents that player controls.

[+2]: Add {R}{R}. Until end of turn, red mana doesn't empty as steps and phases end, and creatures you control gain “{R}: This creature gets +1/+0 until end of turn.”
[–3]: You may cast a monocolored red spell with mana value 6 or less from your hand without paying its mana cost.
[–6]: You may pay any amount of {R}. When you do, Amelie Mayn deals that much damage to each of up to that many different targets.

As long as it's your turn, Ameret is a 4/4 Angel creature with flying, haste, indestructible, and “Whenever Ameret attacks, attach any number of Equipment you control to them.”
[+2]: Create two 1/1 red and white Cleric creature tokens with lifelink.
[–3]: Ameret deals 4 damage to target creature or planeswalker. You gain 4 life.
[–4]: For each creature you control, create a Weapon token and attach it to that creature. (It's an Equipment artifact with equip {2} and “Equipped creature gets +1/+1.”)

Flying
Soldiers and Knights you control get +1/+1.

Reach, vigilance
When Amorphous Tyrant enters, another target creature you control deals damage equal to its power to target creature or planeswalker you don't control.
Evoke {G} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Haste
Frenzy 3 (Whenever this creature attacks and isn't blocked, it gets +3/+0 until end of turn.)
Whenever Anaz, Bloodmother attacks, create a 2/1 red Lizard creature token with frenzy 2 that's tapped and attacking.

Look at the top seven cards of your library. Put two of them into your hand and the rest into your graveyard.

At the beginning of your upkeep, create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)
{5}{W}{W}, Sacrifice three Idols: Return target creature card from your graveyard to the battlefield with three +1/+1 counters on it.

Trample
When Ancient Pillan enters, it fights up to one target creature an opponent controls.

Ward {3}

When Ancient of the Glade enters, put a +1/+1 counter on each other creature you control.
{2}, Remove a +1/+1 counter from a creature you control: That creature gains indestructible until end of turn.

Flying
When Angel of Despair enters, destroy target permanent.