msem-instigator

When Cryptic Sentinel enters, attach any number of target Auras you control to Cryptic Sentinel.
{G}{W}, Sacrifice an Aura: Tap Cryptic Sentinel. It gains indestructible until end of turn.

{T}: Add {C}.
{3}{W}, {T}: Create a 1/1 white Peasant creature token.
Whenever you attack with five or more creatures, you may pay {1}{W}{W} and exile this land. When you do, attacking creatures get +1/+1 until end of turn.

Enchant creature
When Mystic's Mantle enters, draw a card.
Enchanted creature gets +1/+1.
Mirage {G} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)

Whenever you cast a spell, you may pay {1}. If you do, Wizened Tortle explores. (Reveal the top card of your library. Put it into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then you may put that card in your graveyard.)

Whenever Archlegislator attacks, adjudicate. (Create a white Aura enchantment token with enchant creature and “Sacrifice this token: Untap enchanted creature” attached to target creature.)
{3}{R}{R}, {T}, Sacrifice an Aura: Gain control of target creature until end of turn. Untap that creature. It gains haste until end of turn.

Haste
Whenever Malformed Mongrel deals combat damage to a player, discard a card.

Haste
{6}{R}: Diasune Immolator deals 4 damage to target player or planeswalker.

Enchant creature
When Mesmerizing Shimmer enters, untap enchanted creature. It gains haste until end of turn.
You control enchanted creature.
Mirage {2}{U}{R} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)

Return target nonland permanent to its owner's hand. Then that player discards a card.

When King of Bones enters, exile up to ten target creature cards in graveyards. Each opponent loses X life and you gain X life, where X is the number of cards exiled this way.

Choose any number —
• Each player loses X life.
• Each player discards X cards.
• Each player sacrifices X creatures.
• Each player sacrifices X lands.

When Intrepid Shieldmate enters, target creature gets +1/+1 until end of turn.

Enchant creature
You choose whether enchanted creature attacks each combat rather than its controller (after its controller chooses which of their other creatures attack. That player still chooses the player or planeswalker it attacks.)

All creatures get -2/-2 until end of turn. If a creature an opponent controls would die this turn, exile it instead.

At the beginning of each combat, if you control a creature with flying, Magnific Wilderkin gets +1/+1 and gains flying until end of turn. The same is true for first strike, double strike, deathtouch, haste, hexproof, indestructible, lifelink, menace, reach, trample, and vigilance.

Krismite Shard enters tapped.
{1}, {T}, Sacrifice Krismite Shard: Aetherize target creature you control. (To aetherize, create a token that's a copy of it, then exile that token.)

Whenever a creature you control enters, you may have it get +1/+1 until end of turn. If you do, it fights target creature. (Each deals damage equal to its power to the other.)

Serene Hart can't be blocked by creatures with power 4 or greater.

Create three 1/1 white Soldier creature tokens.

At the beginning of your first main phase, you may discard a card. If you do, draw a card and create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)
At the beginning of your end step, if Kessig Tombrobber didn't attack this turn, transform it.

{2/W}{2/W}: Shrapnel Golem deals 3 damage to target creature blocking it.

{2}: Exile up to two target cards in a single graveyard. If two creature cards were exiled this way, create a 1/1 blue Elemental creature token with flying.

Trample

Defender
Foliage Hunter has deathtouch as long as you've cast a spell this turn.

When Ruins' Reward enters, draw a card, then discard a card.
{T}: Add one mana of any color.