msem-instigator

At the beginning of your upkeep, each player loses 3 life unless they sacrifice a creature.
Sacrifice a creature: Fateseal 1. (Look at the top one cards of an opponent's library, then put any number on the bottom and the rest on top in any order.)

Enchant player
At the beginning of enchanted player's end step, if they cast a spell this turn, they lose 1 life.

First strike, haste
Whenever Lothaire attacks, create a 0/0 colorless Reflection creature token that's tapped and attacking. Creatures you control get +1/+1 until end of turn.
{2}{R}{W}: Put a +1/+1 counter on each creature you control.

Flying
Whenever Archon of Inspiration attacks, add three mana in any combination of colors at the beginning of your next main phase.

Trample
Lotusleaf Blade gets +1/+1 as long as you control another Warrior.

Whenever you sacrifice a permanent, you may put a -1/-1 counter on target creature.

At the beginning of your upkeep, sacrifice a non-Snake creature or Boon of the Pacts. Then create a 1/1 black Snake creature token with deathtouch.
At the beginning of your draw step, draw an additional card.
Spells you cast cost {1} less to cast.

Moonlight Stag has vigilance as long as it has a +1/+1 counter on it.

Whenever Merciless Bandit or another creature you control dies, each opponent loses 1 life and you gain 1 life.

Create two 1/1 blue Elemental creature tokens with flying.
Reconstruct {7}{U} (You may cast this from your graveyard for its reconstruct cost reduced by the mana value of a permanent you sacrifice as you cast it this way. Then exile this.)

Return target creature to its owner's hand. That player can't cast spells with the same name as that creature during their next turn.

Reveal the top five cards of your library. You may put an instant or sorcery card from among them into your hand. Put the rest into your graveyard.

Harmony — Create a colorless artifact token named Lotus Petal with “{T}, Sacrifice this artifact: Add one mana of any color.”
When Bouquet Singer enters, harmonize. (Trigger up to one harmony of one permanent you control.)

Enchant creature
Enchanted creature doesn't untap during its controller's untap step unless its controller controls no other creatures.

Enchant player
When Curse of Life's Cycles enters, destroy target creature enchanted player controls.
Concord — At the beginning of enchanted player's upkeep, if there are four or more card types among permanents you control, that player loses 1 life and you gain 1 life.

When Powercell Cultivator enters, create a tapped colorless Powercell artifact token with “{T}: Add {C}.”
Artifacts you control have “{T}: Add one mana of any color.”

Enchant creature
When Hannaru's Courage enters, create a 1/1 white Soldier creature token with vigilance.
Enchanted creature gets +1/+1 and has vigilance.

Whenever a player looks at one or more cards in your library or searches your library, Lavamind Elemental deals 2 damage to that player. (This includes you.)
At the beginning of your end step, look at the bottom card of your library. You may put it on top of your library.

{T}: Add {C}.
{3}{G}: Until end of turn, Damian's Undercity becomes a 2/2 creature. It's still a land. It has lifelink if {W} was spent to activate this ability, gets +0/+3 if {U} was spent, and has deathtouch if {B} was spent.

Double strike, haste

Whenever a creature you control enters, you may have it deal damage equal to its power to another target creature or planeswalker.
I, II, III — Exile the top two cards of your library. You may put a creature card from among them onto the battlefield with a +1/+1 counter on it. It gains haste.
IV — Creatures you control get +3/+3 and gain trample until end of turn.

Haste
Deploy 5 (As this enters, you may tap any number of other creatures you control with total power 5 or more.)
When Line Officer enters deployed, it deals 3 damage to each creature your opponents control.

When Ulek Elder enters, look at the top card of your library. You may put it into your graveyard.

Jara Favored gets +2/+2 as long as you've lost life this turn.

Converge — Admin of Asthenia enters with a +1/+1 counter on it for each color of mana spent to cast it.
Admin of Asthenia can't attack unless its power is 4 or greater.