msem-instigator

{T}, Pay 1 life: Add one mana of any color.

Equipped creature gets +2/+2 and has poisonous 2. (Whenever this creature deals combat damage to a player, that player gets two poison counters.)
Whenever equipped creature attacks, create a 1/1 green Snake creature token with poisonous 1 that's tapped and attacking. Exile that token at end of combat.
Equip {2}

Abandoned Forge enters tapped if you control another nonbasic land.
{T}: Add {R} or {W}.

Whenever you cast an Adventure spell, put a +1/+1 counter on Adventurer Extraordinaire.

Rapport — Whenever Aelinn, Serpent's Voice and at least one other creature you control become tapped, reveal the top card of your library. You may cast that card. If you don't, put it into your graveyard and Aelinn, Serpent's Voice deals 2 damage to each opponent.

Haste
Heroic — Whenever you cast a spell that targets Akroan Siege Captain, put a +1/+1 counter on each creature you control.

Create two 3/1 red and white Goblin Soldier creature tokens with haste. Creatures you control gain indestructible until end of turn.

Whenever Align with Animus Vox enters or you attack with three or more creatures, crystallize. (Put a +1/+1 counter on a creature you control or create a Treasure.)

Flying, first strike, vigilance, trample, lifelink
{4}: Put a +1/+1 counter on Alin and Meva, Warqueens.

Creatures you control gain vigilance until end of turn. After this main phase, there's an additional combat phase followed by an additional main phase.
Compose (Then if you cast this from your hand, exile it and create a Saga token with “r3—You may cast a copy of this card from exile without paying its mana cost.”)

At the beginning of combat on your turn, if there are seven or more loyalty counters on Ameret, they become a 5/5 Angel creature with flying and indestructible until end of turn.
[+1]: Create a 1/1 red and white Cleric creature token with lifelink and haste.
[–X]: Ameret deals X damage to any target. You gain X life.

As long as it's your turn, Ameret is a 4/4 Angel creature with flying, haste, indestructible, and “Whenever Ameret attacks, attach any number of Equipment you control to them.”
[+2]: Create two 1/1 red and white Cleric creature tokens with lifelink.
[–3]: Ameret deals 4 damage to target creature or planeswalker. You gain 4 life.
[–4]: For each creature you control, create a Weapon token and attach it to that creature. (It's an Equipment artifact with equip {2} and “Equipped creature gets +1/+1.”)

Flying, haste
Angel spells you cast cost {1} less to cast.
Other Angels you control get +1/+1 and have haste.

At the beginning of your end step, put an encroachment counter on Approach of Old Lovi, then it deals X damage to any target and you gain X life, where X is the number of encroachment counters on Approach of Old Lovi.

Arid Causeway enters tapped unless you control another Desert.
{T}: Add {R} or {W}.

Arsenal Curator gets +1/+1 as long as you control a Plains.
{2}{W}: Untap target creature you control. It gets +0/+1 until end of turn.

Flying
Whenever August Sunbird attacks, create a token that's a copy of another target creature you control, except it's 1/1, and it's tapped and attacking. Sacrifice the token at the beginning of the next end step.

Avaz Sanctuary enters tapped.
Satrapies you control have “{T}: Add {R} or {W}.”

[+1]: Tap up to one target creature. Azun, Sheriff of Daisite deals 1 damage to each opponent.
[–1]: Exile another target nonland permanent until Azun, Sheriff of Daisite leaves the battlefield.
[–7]: Detain each permanent target opponent controls. (Until your next turn, those permanents can't attack or block and their activated abilities can't be activated.)

{T}, Pay 1 life: Add {R} or {W}.
{1}, {T}, Sacrifice Backstage Rooms: Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

When Barbarian Hoarders enters, you may attach target Equipment you control to it.

When Barbarian Intimidator enters, target creature can't block this turn.
When Barbarian Intimidator enters, prevent all combat damage that would be dealt to target creature this turn.

When Batrest's Forgemaster enters, you may search your library for an Equipment card, reveal it, put it into your hand, then shuffle.
Whenever Batrest's Forgemaster attacks, Equipment spells you cast this turn cost {2} less to cast.

Batrest, Fellor Leader gets +1/+1 for each Equipment attached to it.
When Batrest enters, create Astrina, Forged for Glory, a legendary colorless Equipment artifact token with “Equipped creature gets +4/+4 and has first strike and lifelink” and equip {4}. Attach it to Batrest.

Battalion — Whenever Battleborn Brute and at least two other creatures attack, Battleborn Brute gets +2/+2 until end of turn. Untap it.