msem-instigator

At the beginning of combat on your turn, you may have Regurgitator Ooze consume. If you do, it gets +2/+2 until end of turn. (To consume, sacrifice another creature or exile a creature card from your graveyard.)
When Regurgitator Ooze dies, return a card exiled with it to its owner's hand.

First strike
Whenever a nontoken creature you control leaves the battlefield, you may pay {W}. If you do, create a 1/1 colorless Spirit creature token.

At the beginning of your upkeep, you may put a +1/+1 counter on target creature.

Arm target creature you control. It deals damage equal to its power to any target. (Create a colorless Equipment artifact token with “Equipped creature gets +1/+0” and equip {2}, then attach it to that creature.)

I — Search your library for a basic land card, reveal it, put it into your hand, then shuffle.
II — You may put a land card from your hand onto the battlefield.
III — Lands you control gain “{T}: Add one mana of any color” until end of turn.

Target player loses 3 life and you gain 3 life. (Then exile this card. You may cast the creature later from exile.)

Once each turn, when you activate a nonmana ability, you may create a tapped 1/1 white Spirit creature token with flying.
{4}{W}{U}: You gain 1 life and draw a card.

When Artian, Phyrexian Architect enters, search your library for a land card, put it onto the battlefield, then shuffle.
At the beginning of your upkeep, put a corruption counter on a land you control. Then create a 1/1 colorless Phyrexian artifact creature token for each land you control with a corruption counter on it.

Counter target spell with mana value 3 or less. If a spell is countered this way, return it to its owner's hand instead of putting it anywhere else.

Spire Runner can't be blocked.
Whenever Spire Runner deals combat damage to a player, you may draw a card. If you do, discard a card.

Flying
Whenever Starborne Hellkite attacks, choose two—
• Starborne Hellkite deals 4 damage to any target.
• Destroy target artifact or land.
• Creatures you control get +2/+0 until end of turn.

Enchant creature
Embody (Enchanted creature is a copy of this card except for its types.)
As long as Legend of the Weary is tapped, creatures you don't control get -1/-1.

If a nontoken creature you control would die, you may exile it instead. If you do, create two 1/1 white Spirit creature tokens with flying.

Whenever equipped creature attacks or blocks, you gain 2 life.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Whenever Rhudai Swathcutter attacks, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Alpha (You may have this creature enter with a +1/+1 counter on it. If you do, it becomes alpha and can only attack alone.)
Whenever a creature you control attacks alone, target creature an opponent controls blocks this turn if able.

Target creature you control gets +2/+2 until end of turn. It fights target creature with flying you don't control.

When Confining Priest enters, exile another target creature with power 4 or less an opponent controls until Confining Priest leaves the battlefield. (That creature returns under its owner's control.)

{T}: Add {C}.
{1}, {T}: Add one mana of any color. When this mana is spent to cast a spell that shares a color with a legendary creature you control, scry 1.

While an opponent is choosing targets as part of casting a spell they control or activating an ability they control, that player must choose at least one Flagbearer on the battlefield if able.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Equipped creature gets +1/+0 and has menace.
Equip {2}

Target opponent reveals their hand. You choose a creature card from it. That player discards that card.

Whenever a creature you control becomes tapped, exile the bottom card of your library. You may put it on top of your library. If you don't, Flames of the Forge deals 1 damage to target opponent or planeswalker.

Choose one —
• Change all targets of target spell or ability.
• All damage that would be dealt to target creature this turn is dealt to another target creature instead.

Vigilance, reach
When Treeline Archer enters, mill four cards.
{5}{G}: Transform Treeline Archer. Activate only if it's attacking.