msem-instigator

Target player discards two cards.
Fabled {3}{B}{B} (Then if you cast this for its fabled cost, put it onto the battlefield transformed attached to that player.)

Other Rebel creatures you control get +0/+1.
When Veteran Renegade enters, create a 1/1 white Rebel creature token.

Whenever another Avatar you control enters, upgrade it and Experienced Mentor. (Give each one of the listed counters it doesn't already have. Upgrades are independent.)
• +1/+1
• First strike
• Vigilance

When Wretched Spawn enters, you may return target permanent to its owner's hand. If you do, that player discards a card.
Unearth {4}{U}{B} ({4}{U}{B}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the end step or if it would leave the battlefield. Unearth only as a sorcery.)

As an additional cost to cast this spell, discard a card.
Draw two cards.

Exile target creature. At the beginning of the next end step, return that card to the battlefield under its owner's control with your choice of X counters on it from among +1/+1, flying, first strike, and/or vigilance.

When Remnant of Lost Times enters, scry 1.
{2}, Sacrifice Remnant of Lost Times: Draw a card.

When Snarling Devil enters, create four 1/1 black Possum Dog creature tokens.
At the beginning of each upkeep, put your choice of a +1/+1, lifelink, menace, trample, or vigilance counter on a token creature you control.

Trample
Wanderlust — Whenever Akkrixian Assailants attacks, if you control four or more differently named lands, put a +1/+1 counter on it.

Enchant creature
When Twinklewings enters, draw a card.
Enchanted creature has flying.

Indestructible
Whenever Anku the Primordial attacks, defending player sacrifices an artifact, a creature, an enchantment, and a land.

Flying
Other creatures you control with flying get +1/+1.

[+2]: Until end of turn, up to one target creature you control gets +3/+3 and gains trample and vigilance.
[–2]: Destroy target artifact, enchantment, or tapped creature.
[–3]: Create a 1/1 green Insect creature token, a 2/2 white Cat creature token, and a 3/3 red Ox creature token.
[–8]: Until end of turn, creatures you control get +X/+X and gain trample and vigilance, where X is the number of creatures you control.

Enchant creature
Enchanted creature gets +1/+3 and has flying.

When Lich's Grimoire enters, create a 2/2 black Zombie creature token.
{2}{B}, {T}: Target opponent loses 1 life. Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Flash
Flying
Whenever another Spirit you control enters, put a +1/+1 counter on Flickers in the Night.

All creatures get -2/-2 until end of turn. At the beginning of the next end step, if three or more creatures died this turn, create two tapped Treasure tokens.

Long-Lived Prowler gets +3/+0 as long as there are four or more card types among cards in your graveyard.

Abandoned Den enters tapped.
{T}: Add {B}.
{B}, {T}: Target player loses 1 life. Activate only as a sorcery and only if you control a black creature.

Target creature phases out. Its controller sacrifices a creature. (Treat the phased out creature and anything attached to it as though they don't exist until its controller's next turn.)

Gestalt (When this or another creature enters under your control, 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.)
Towering Wickerman can't be blocked by creatures with power 2 or less.
Whenever a creature merges with Towering Wickerman, put two +1/+1 counters on it.

{1}{G}{G}, Sacrifice a creature: Search your library for a creature card with mana value X or less, where X is 1 plus the sacrificed creature's mana value. Put that card onto the battlefield, then shuffle. Activate only as a sorcery.

Defender (This creature can't attack.)
Discard a card: Barge Engulfer can attack as though it didn't have defender until end of turn.

Destroy target creature that was dealt damage this turn. (Then exile this card. You may cast the creature later from exile.)

Enchant opponent
The first time enchanted player chooses targets each turn, reselect each of those targets at random.