msem-instigator

Whenever you make first contact, create a 1/1 white Bird creature token with flying. (You make first contact the first time each turn you cast a spell with a name not in your graveyard or control already.)
Whenever three or more creatures you control deal combat damage to a player, create a token that's a copy of another target permanent you control.

You may put a creature or planeswalker card from your hand onto the battlefield. If it's a creature, it gains haste and indestructible. Return it to your hand at the beginning of your next end step.

Double strike
Improve {1}{R/W} ({1}{R/W}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
At the beginning of combat on your turn, if you control three or more embattled creatures, you may search your library for an artifact, enchantment, or Angel card, reveal it, put it into your hand, then shuffle.

Creatures your opponents control attack each turn if able.
Blocking creatures you control get +4/+0.
{W}: Untap Masha, Hero of Pelastrov.

Creatures you control attacking cause abilities of that creature to trigger as though it entered.
{2}{R}{W}: Target creature gains vigilance and haste until end of turn. After this main phase, there is an additional combat phase followed by an additional main phase.

When you cast this spell, copy it for each Reflection creature you control. You may choose new targets for the copies.
Mirrorstorm deals 1 damage to any target and you gain 1 life.

Cast this spell only during the declare blockers step.
After this step there's an additional declare attackers step followed by an additional declare blockers step. (A creature can't attack or block again if it's already attacking or blocking.)
Draw a card.

Target creature gets +1/+1 until end of turn.
Fabled {2}{R/W}{R/W} (Then if you cast this for its fabled cost, put it onto the battlefield transformed attached to that creature.)

When Monk of Mid-Autumn enters, choose one —
• Put a double strike counter on Monk of Mid-Autumn.
• Destroy target artifact or enchantment.
• Monk of Mid-Autumn deals 2 damage to target tapped creature and you gain 2 life.

Trial 2 (As you cast this spell, an opponent of your choice may pay 2 life. If they don't, they fail the trial.)
When Nascent Adversary enters, if the trial was failed, it gains haste and first strike until end of turn.

At the beginning of combat on your turn, you may attach target Equipment you control to Nina, Master of Arms.
Whenever Nina attacks, the next artifact spell you cast this turn costs {R/W}{R/W} less to cast. (This can reduce the amount of generic mana you pay.)

Target creature you control gains haste until end of turn. Return it to its owner's hand at the beginning of the next end step.

Prowess
When One of Purpose enters, if you cast it, create a Function token with “If you cast this spell from your hand, exile it. You may cast it from exile until the end of your next turn.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Lifelink
Whenever Painstriker attacks, it deals 2 damage to target creature defending player controls.

Other creatures you control get +1/+0.
{R}{W}: Create a 1/1 red and white Warrior creature token. That token gains haste. Exile it at the beginning of the next end step. Activate only as a sorcery.

Whenever Perfecting Forgemaster enters or attacks, you may sacrifice an artifact. If you do, look at the top six cards of your library. You may reveal an Equipment card from among them. Put it onto the battlefield if its mana value is less than or equal to the sacrificed artifact's mana value. Otherwise, put it into your hand. Then shuffle.

When Performers of Purpose enters, if a permanent you controlled left the battlefield this turn, create a 1/1 colorless Construct Actor creature token.
As long as it's your turn, Performers of Purpose has first strike.

Double strike, menace
{R}{W}, Exile Picturesque Champion from your graveyard: Target creature you control gains double strike and menace until end of turn. Activate only as a sorcery.

[+1]: Create a 1/1 white Cat creature token with lifelink.
[–1]: When you next activate a nonmana ability of target permanent this turn, copy that ability. You may choose new targets for the copy.
[–7]: Exile up to seven target permanents. Return those cards to the battlefield under their owner's control at the beginning of the next end step.

Archive 2 (As this enters, shuffle the top two cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
{R}{W}: Put a nontoken artifact or creature you own on the bottom of the archived library. Create a token that's a copy of it.

Codex — Eleventh Hour Breakthrough; Mentorb; Ostracizer Orb; Possibility Engine; Sealed Riftway; Self Replication. (As this enters, conjure its contents into a shuffled face-up additional library.)
{T}, Sacrifice an artifact: Draw a card from the codex's library.

[+1]: Artifact creatures you control get +1/+1 and gain haste until end of turn.
[–X]: You may cast an artifact card with mana value X or less from your hand without paying its mana cost. If it has {X} in its cost, {X} is X.
[–6]: Choose a number. For each artifact you control with the mana value equal to the chosen number, create a token that's a copy of it.

Flash
When Pivot-Fist Meditant enters, choose a creature you control. Whenever that creature is dealt damage this turn, it deals that much damage to any other target.

{X}, {T}, Sacrifice an artifact: Exile target artifact card in your graveyard with mana value X. Create a token that's a copy of it. Activate only as a sorcery.

Harmony — Creatures you control get +1/+0 and gain vigilance until end of turn.
When Plume de Val Singer enters, harmonize. (Trigger up to one harmony of one permanent you control.)