msem-instigator

[+1]: Tanya, the Mooncursed becomes a legendary 3/1 red Werewolf creature with first strike until end of turn.
[–2]: Tanya, the Mooncursed deals 3 damage to target creature or planeswalker.
[–4]: Destroy target nonbasic colorless permanent.

As an additional cost to cast this spell, return a creature you control to its owner's hand or pay {2}.
Counter target spell.

When Soulblade enters, exile target creature card with mana value 3 or less from your graveyard.
Whenever equipped creature attacks, create a token that's a copy of a card exiled with Soulblade that's tapped and attacking. Exile the token at end of combat.
Equip {1}

When Mourners of Mervin enters, you may sacrifice a creature or enchantment. If you do, creatures you control get +1/+1 and gain vigilance until end of turn.

Trample
Whenever you cycle Long-Term Method Actor or it attacks, proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)
Basic landcycling {1}{G} ({1}{G}, Discard this card: Search your library for a basic land card, reveal it, and put it into your hand, then shuffle.)

Enchant creature
Embody (Enchanted creature is a copy of this card except for its types.)
As long as Legend of the Weary is tapped, creatures you don't control get -1/-1.

When Silt Miner enters, you may salvage an artifact or creature card. (Exile one from your graveyard until this creature leaves the battlefield. Whenever this creature deals combat damage to a player, put a card it salvaged into your hand.)

When Harpooned Bubbledomer enters, mill four cards.
Harpooned Bubbledomer gets +2/+0 and has menace as long as there are four or more card types among cards in your graveyard.

When this creature enters, create two 1/1 white Peasant creature tokens.
Whenever this creature attacks, you may pay {4}{G/W}. If you do, attacking Citizens and Peasants get +1/+1 until end of turn.

Choose one —
• Creatures your opponents control get -1/-1 until end of turn.
• Harmonize twice. (To harmonize, trigger up to one harmony of a permanent you control.)

Discard your hand. Creatures you control get +X/+0 and gain first strike until end of turn, where X is the number of cards discarded this way.

Rhapsody {5}{R}{W} (Pay {5}{R}{W} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Whenever a creature you control with power 4 or greater attacks, look at the top four cards of your library. You may cast a nonland card with mana value 3 or less from among them without paying its mana cost. Put the rest on the bottom of your library in a random order.

Concord — Silt-Trench Brute gets +3/+3 and has trample as long as there are four or more card types among permanents you control.

Explorer's Ascent enters tapped.
{T}: Add {W}.
{T}: Target creature you control gets +1/+1 until end of turn.

Flying, deathtouch

Trample
Augmented — Whenever you cast a spell, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, put a +1/+1 counter on Isolated Guardian. It loses this ability and gains “Whenever this attacks, put two +1/+1 counters on each of up to two target creatures.”

Trample
Chosen one ({W}{U}{B}{R}{G}: Transform this permanent.)

Surveil 1, then draw a card.
Flashback—{2}{B}, Pay 1 life. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Tap up to one target nonbasic permanent. It doesn't untap during its controller's next untap step.
Coalesce {5}{U} (You may cast this from your graveyard for {5}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Exile target nonland permanent. For each of its colors, its controller creates a 1/1 colorless Spirit creature token.

{1}{U}: Mercurial Merfolk gets +2/-2 until end of turn.
When Mercurial Merfolk dies, draw a card.

Puzzlebox (Begin the game with this and another card you own from outside the game in the command zone, locked. That card is face down until you unlock this.)
{1}, Sacrifice two Clues: Unlock Hall of Lost Histories and put the revealed card into your hand.

When Wild Hermit dies, create a 2/2 white Cat creature token.
Revive—{3}{G}{G}, Sacrifice a creature. ({3}{G}{G}, Sacrifice a creature, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

Target player loses 3 life.

{T}: Add {C}.
{T}: Choose a color from among permanents you control. Add one mana of that color.