msem-instigator

Rather than pay the mana cost for a spell, its controller may discard a card that shares a color with that spell.
Whenever an opponent casts a spell, counter that spell unless they pay 5 life.

Reach
Risen Lumberknot gets +5/+5 as long as you control eight or more lands.
Invocation — Whenever you spend four or more mana to cast a spell or activate an ability during your turn, untap all lands you control. This ability triggers only once each turn.

Grasp of the Sands deals 5 damage to target attacking or blocking creature. Scry 1.

Scry 2, then create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)
Monument {2}{R} (You may cast this transformed from your graveyard for its monument cost. Exile it if it would leave the battlefield or not resolve.)

If Madame Beatrice would leave the battlefield, exile her instead.
Whenever one or more creatures you control deal combat damage to a player, that player reveals their hand. You may cast a card from their hand without paying its mana cost.

This spell costs {1} less to cast for each card type among cards in your graveyard.
Deathtouch

Search your library for a basic land card, reveal it, put it into your hand, then shuffle. You gain 2 life.

When Duchess Odelia VII enters, search your library for a nonland permanent card with mana value 1 or less, reveal it, put it into your hand, then shuffle.

This spell costs {2} less to cast if you activated an ability that's not a mana ability this turn.
Searing Grace deals 3 damage to any target.

({T}: Add {R} or {G}.)
Practice Range enters tapped unless you control two or more basic lands.

Counter target creature spell.
Permutate. (You may remove a counter from a creature you control. If you do, put two +1/+1 counters on a different creature you control.)

As an additional cost to cast this spell, you may sacrifice a creature. If you do, this spell costs {3} less to cast.
Create two 3/3 white Construct enchantment creature tokens.

Choose one —
• Kilnfire deals 1 damage to each creature and planeswalker target player controls.
• Destroy target artifact.

Destroy target creature or planeswalker with mana value 2 or less. Create a tapped Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

Look at target player's hand. Draw two cards, then discard a card.

At the beginning of your end step, you may put a progress counter on Snowclearer.
[PROGRESS 1-2] Sacrifice Snowclearer: Add {C}.
[PROGRESS 3+] Sacrifice Snowclearer: Add two mana of any one color.

Flying
{1}, Sacrifice a creature: Put a +1/+1 counter on Bloodthirsty Manticore. It gains indestructible until end of turn. Tap it.
Surpass {4}{B}{R} ({4}{B}{R}: Transform this creature. This costs {1} less to activate for each counter on it. Activate only as a sorcery.)

Destroy target artifact, enchantment, or creature with flying.

Flash
Whenever Operative POSH attacks or you cast a green or red spell, exile up to one target nontoken permanent. Return that card to the battlefield under its owner's control at the beginning of the next end step.

This spell costs {1} less to cast if it targets a creature with power 3 or less.
Destroy target attacking or blocking creature.

When Poisoned Shiv enters, destroy target creature or planeswalker.
Equipped creature gets +2/+0 and has deathtouch.
Equip {2}

When this creature enters, each player discards a card. Then return an instant or sorcery card from your graveyard to your hand.

Each player chooses a creature with the least power among creatures they control. Then destroy the rest.

Destroy target creature.
Create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)

Tithe (As you cast this spell, you may tap three artifacts and/or creatures you control.)
Croakfolk Marsh-Baron enters with X +1/+1 counters on it. If its tithe was paid, it enters with twice X +1/+1 counters instead.