msem-instigator

[+1]: The next instant or sorcery spell you cast this turn costs {1} less to cast.
[–4]: Until end of turn, whenever you cast an instant or sorcery spell, Merkurio deals 2 damage to any target.
[–8]: Exile the top seven cards of your library. You may cast any number of instant and sorcery cards from among them without paying their mana costs.

Motivate 1 (When this creature enters, you may motivate target creature with less power than this by putting a +1/+1 counter on it.)
When Merthilios' Escort motivates a creature, that creature gains first strike until end of turn.

Enchant creature
When Mesmerizing Shimmer enters, untap enchanted creature. It gains haste until end of turn.
You control enchanted creature.
Mirage {2}{U}{R} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)

Enchant creature
Enchanted creature can't be blocked.
{1}{R}: Enchanted creature gets +1/+0 until end of turn.

Whenever another artifact you control enters, put a +1/+1 counter on Metalwork Machinist.

Artifact spells you cast cost {1} less to cast.
{2}, Sacrifice an artifact: Target creature gains deathtouch until end of turn.

When Miasma Spewer enters, you may sacrifice a permanent. When you do, Miasma Spewer deals 1 damage to each opponent and each creature and planeswalker they control.

Flash

Each player loses 2 life, discards two cards, sacrifices two creatures, then sacrifices two lands.

Choose one—
• Destroy target artifact.
• Target creature gets +4/+4 until end of turn.

Choose one —
• Destroy target artifact.
• You gain 4 life.

Reveal the bottom two cards of your library. You may put one of those cards into your hand. If you do, target creature gets +X/+X until end of turn, where X is that card's mana value.

Until end of turn, target creature gains double strike and damage dealt by it can't be prevented.
Fuse (You may cast one or both halves of this card from your hand.)

At the beginning of your upkeep, you gain 1 life for each creature you control.
{3}{W}: Create a 1/1 white Soldier creature token. Activate only if you have the highest life total among all players.

Each opponent discards all the cards in their hand, then draws that many cards. You discard your hand, then draw cards equal to the number of cards your opponents drew this turn.

Whenever you cast an instant or sorcery spell, target player mills a card.

Whenever a source you control deals noncombat damage to a player, put a +1/+1 counter on Mindblaze Pyromancer.

Mindhunter Grizzly can't attack or block unless you scried this turn.
{5}{U}: Scry 1.

Flying (This creature can't be blocked except by creatures with flying or reach.)
Whenever Mindscreech Drake deals combat damage to a player, that player mills three cards.

Equipped creature gets +1/+1. If it's a token, it gets +3/+3 instead.
Equip {2}

{W}, {T}: Remove target creature you control from combat.

Shimmer (Whenever this creature attacks, create a tapped and attacking token that's a copy of it. Exile the token at the beginning of the end step.)
{2}{G}, {T}: Create a token that's a copy of target creature token.

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.

Reach
Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Other Elementals you control get +1/+1 as long as Miroran Skycatcher has a +1/+1 counter on it.