msem-instigator

Whenever Merchant of Flesh or another creature you control dies, create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)
{B}, Sacrifice two Treasures: Each opponent sacrifices a creature.

{T}: Add {C}.
{1}, {T}: Add {R}{W}.

This spell costs {1} less to cast for each permanent you control that's an artifact and/or a token.
When Kellythross's Collector enters, you may return another target nonland permanent to its owner's hand.

{2}, {T}: Exile target creature. Return that card to the battlefield under its owner's control at the beginning of the next end step. Activate only as a sorcery.

Unassuming Waif can't be blocked.
Unassuming Waif gets +1/+0 for each other Warrior you control.

Trample
{T}: Add {C}.
At the beginning of your upkeep, you may pay {2}. When you do, Blundering Clocktower becomes a creature in addition to its other types until the beginning of your next end step. End the turn.

Haste
Sacrifice a land: Trail Blazer explores. You may put a basic land card from your hand onto the battlefield tapped. (Reveal the top card of your library. Put it into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then you may put that card in your graveyard.)

Vigilance
{T}: Target instant or sorcery card in your graveyard with mana value 3 or less gains flashback {0} until end of turn. Activate only as a sorcery. (You may cast that card from your graveyard for its flashback cost. Then exile it.)

Other Angels and Nephilim you control get +1/+1.
As long as you control three or more other Angels and/or Nephilim, Herald of Atieh gets +1/+1 and has flying.

{3}{B}{B}: Return target Zombie creature card from your graveyard to the battlefield.
Whenever another creature you control enters from a graveyard or you revive a creature token, that creature gets +2/+0 and gains haste and menace until end of turn.

Deathtouch
When Vizier of Lies enters, you may return target instant or sorcery card from your graveyard to your hand.

Reach
Whenever you cast a noncreature spell, you may pay {R}. If you do, target creature can't block this turn.

Menace
Augmented — When Gravitational Ripper enters, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, target opponent sacrifices a creature. If they can't, they discard a card.

Target opponent discards a card. If a creature card was discarded this way, that player loses 3 life. If a land card was discarded this way, add {B}{B}. If a noncreature, nonland card was discarded this way, draw a card.

Draw three cards. Discard two cards at the beginning of the next end step.

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.)

Harmony — Destroy target artifact or enchantment.
When Rejoicing Aristocrats enters, harmonize. (Trigger up to one harmony of one permanent you control.)

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.

When Hunting Ground enters, create four 1/1 green Saproling creature tokens.
Whenever a creature you control dies, creatures you control get +1/+1 until end of turn.

As an additional cost to cast this spell, you may pay {2} and tap an untapped Rogue you control. When you do, copy this spell and you may choose new targets for the copy.
Target creature gets -2/-2 until end of turn.

Royster Hounds can't be blocked by creatures with power 2 or less.

{2}: Exile up to two target cards in a single graveyard. If two creature cards were exiled this way, create a 1/1 blue Elemental creature token with flying.

Interan Soothsayer gets +1/+1 for each other green creature you control.
{G}, {T}: Put a +1/+1 counter on target green creature.

Whenever Orria Mirrorpelt becomes the target of a spell, exile that spell. If Orria Mirrorpelt was its only target, copy it for each other creature target player controls. Each copy targets a different one of those creatures.