msem-instigator

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Enchanted creature gets +1/+3.
Whenever enchanted creature attacks, you gain 1 life.

Gestalt (When this or another creature you control enters, you may merge it with the one in play, keeping counters and attachments. They become the permanent on top plus all abilities from under it.)
This permanent gets +2/+2 for each card and token merged with it.

Distribute three +1/+1 counters among one, two, or three target creatures you control.

Target creature gains indestructible until end of turn. Whenever that creature perseveres this turn, create a 1/1 white Nymph creature token. (A creature perseveres when it survives damage.)

Put a +1/+1 counter on target creature you control.
Monument {1}{G} (You may cast this transformed from your graveyard for its monument cost. Exile it if it would leave the battlefield or not resolve.)

Whenever one or more creatures an opponent controls attack you or a planeswalker you control, that player gets a poison counter.

Glitch {2} (Remove one [restriction] for each time you pay the glitch cost.)
Target [attacking] creature gets +2/+2 and gains indestructible until end of turn.

Enchant creature
Enchanted creature gets +3/+3 and has “{G}: Regenerate this creature.”

At the beginning of your upkeep, create two 1/1 colorless Construct artifact creature tokens, then you gain life equal to the number of artifacts and enchantments you control.

Enchant land (Target a land as you cast this. This card enters attached to that land.)
Enchanted land has “{T}: Add one mana of any color” and “At the beginning of each upkeep, untap this land.”

When Blessing of Roya enters or whenever you cast a spell from a graveyard, you gain 5 life and you mill five cards. Then you may put a card from your graveyard on the bottom of your library.

Whenever you cast an instant or sorcery spell from exile, copy it. You may choose new targets for the copy.

Up to two target creatures you control each get +2/+0 and gain first strike and haste until end of turn.
Orchestrate—Tap an untapped red and white creature you control or an untapped red creature you control and untapped white creature you control. (You may exile this card from your hand anytime you could cast a sorcery for its orchestrate cost. When you next resolve a spell, you may cast this from exile without paying its mana cost.)

Creatures you control get +2/+2 until end of turn.

{T}: Add {B} or {G}.
{B}{G}, {T}: Target creature gets +1/+1 until end of turn.

{1}{B}: Blightcaller Shaman gains deathtouch until end of turn.

Trample
{1}{G}: Put an overgrowth counter on target creature you control. As long as it has an overgrowth counter on it, it has base power and toughness 8/8.

Equipped creature gets +2/-1.
Equip {1}

Haste
When Blighted Dullahan dies, you draw a card and you lose 1 life.

{1}{B}, {T}: Target creature gets +2/+2 and gains winnow until end of turn. (Damage dealt to it also causes its controller to lose that much life.)
{3}{B}{B}, {T}: Target creature gets -2/-2 and gains winnow until end of turn.

Whenever one or more creatures attack you, you may put a -1/-1 counter on target creature.

Blighted Unicorn can't block.
Ride {3}{B} ({3}{B}: Transform this and attach it to target creature you control without a Steed. Ride only as a sorcery.)

When Blighting Ooze enters, put a -1/-1 counter on each of up to X target creatures.
As long as Blighting Ooze is on the battlefield, it has all activated abilities of each creature with a -1/-1 counter on it.

Sacrifice a creature: Put a +1/+1 counter on Blightroot.
Sacrifice a land: Blightroot gains indestructible until end of turn.

Flash
Blind Blackguard can't block.
When Blind Blackguard enters, target player draws a card, then reveals their hand. You choose a nonland card from that player's hand, then that player puts the chosen card on the bottom of their library.