msem-instigator

Creatures with power less than or equal to the number of creatures in Wildershrine Elder's pack can't block it. (Two or more creatures you control with equal power are in a pack.)

Flash
When Daughter of Tempests enters, target creature an opponent controls gets -2/-0 until end of turn.
Attain {3}{U} ({3}{U}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

[+1]: Mill two cards. Untap up to one target creature or land.
[–2]: Return target creature or land card from your graveyard to your hand.
[–X]: You may sacrifice a creature. If you do, search your library for a creature card with mana value X or less, put it onto the battlefield, then shuffle.

Enchant creature
Enchanted creature gets +1/+1 for each artifact and/or enchantment you control.

Target opponent sacrifices a creature with the greatest power among creatures that player controls.
Fabled {3}{B}{B} (Then if you cast this for its fabled cost, put it onto the battlefield transformed attached to that player.)

Whenever a creature blocks or becomes blocked by Faceless Virtue, that creature loses all abilities until end of combat.

At the beginning of your second main phase, you may return a creature you control to its owner's hand. If you do, add {G}{U}.

When Core Paradigm enters, conjure five cards named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)
Up to three times each turn, you may cast a sorcery spell without paying its mana cost.

Distorted (This creature can be blocked by tapped creatures but not untapped creatures.)
As you choose targets for an instant or sorcery spell, choose up to one additional target.
At the beginning of combat on your turn, gain control of another target creature until end of turn. Untap that creature. It gains haste until end of turn.

Lifelink
If a source would deal damage to a player, you may prevent X of that damage, where X is the number of +1/+1 counters on Mending Caretaker.

Trample
When Rundfora Communionist enters, return a creature you control to its owner's hand.
Creature spells you cast cost {1} less to cast.

Wu Xing (Add effects based on the number of colors of mana spent to cast this spell.)
1 | Return target creature card from your graveyard to the battlefield.
5 | It gains vigilance, trample, lifelink, indestructible, and haste until end of turn.

Flying
Tawny Prophet enters with three +1/+1 counters on it.
{W/U}, Remove a +1/+1 counter from Tawny Prophet: Scry 1, then draw a card.

{6}{U}: Brume Trench-Thrasher can't be blocked this turn. This ability costs {1} less to activate for each instant and sorcery card you own in exile and in your graveyard.

At the beginning of your upkeep, if six or more cards are in your graveyard, you may transform Scuttling Gnat.

Menace
As long as there are two or more cryptic cards in your graveyard, Fierce Raider has double strike. (Artifacts, enchantments, and modal spells are cryptic.)
Cryptic spells you cast can't be countered.

Exile target blocking or blocked creature. If that creature had a +1/+1 counter on it, you gain life equal to its power.

Rapport — Whenever Ainok Lout and at least one other creature you control become tapped, Ainok Lout gets +2/+0 until end of turn.

As long as Champion of Ideals has one or more +1/+1 counters on it, it's an Angel with base power and toughness 4/4, flying, vigilance, and lifelink.
{3}{G}: Judge target creature you control. Activate only as a sorcery. (Honor it by putting a +1/+1 counter on it or condemn it by sacrificing it to draw a card.)

Whenever one or more artifacts you control enter, put a +1/+1 counter on Octopus Shiny-Grabber and you gain 1 life.

Menace

Whenever you cast an artifact spell, scry 2.

Whenever a nontoken creature you control enters, if it shares no creature types with other creatures you control, draw a card.

Whenever Arena Challenger deals damage to a creature, upgrade it. (Give it one of the listed counters it doesn't already have.)
• +1/+1
• First strike
• Prowess

When Glowskate Channeler enters, create a green Aura enchantment token named Manta's Wings attached to target creature. The token has enchant creature and “Enchanted creature gets +2/+2.”