msem-instigator

Whenever you create one or more tokens, put a +1/+1 counter on target creature you control.
{2}{G}{W}: Create a 0/1 green Plant creature token.

Double strike
Engage (This creature must be blocked each combat if able.)
{1}{R}: Balanced Blade gets +1/+0 until end of turn.

Prowess
Whenever Balefire Conjurer attacks, you may pay {1}{R}. If you do, exile the top card of your library. You may play that card until the end of your next turn.

Menace
As long as Balefire Harbinger is attacking, creatures in its pack can't be blocked unless defending player pays {1} and 1 life for each creature they control that's blocking one of those creatures. (Two or more creatures you control with equal power are in a pack.)

Flying, deathtouch

Whenever Baljurn, the Runelord or another nontoken artifact or enchantment you control enters, create a 0/0 blue Construct artifact creature token. Put a +1/+1 counter on each artifact and/or enchantment creature you control other than Baljurn.

Target creature gets +1/+0 and can't be blocked this turn.
Showcase {2}{U} (Then if you cast this for its showcase cost, create a 1/1 red Bard creature token that can't block and exile this. Whenever it attacks, you may cast a free copy of this.)

Haste (This creature can attack and {T} as soon as it comes under your control.)
{1}{U}: Balloon Dragoon gains flying until end of turn.

This spell costs {U} less to cast if you dealt combat damage to a player this turn with a Rogue.
Flying
When Balloon Voyager enters, draw a card.

Ward {3} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {3}.)
Lifecycle {3} ({3}, Discard this card: Create two tapped 1/1 colorless Elemental creature tokens.)

At the beginning of combat on your turn, if there are five or more creature types among creatures you control, creatures you control get +2/+0 and gain menace until end of turn.

Equipped creature gets +3/+0 and has vigilance.
Equip {3}

Whenever equipped creature attacks, it gains deathtouch until end of turn.
Sacrifice Bandit's Dagger: Target player dealt damage by equipped creature this turn reveals their hand. You choose a nonland card from it. That player discards that card.
Equip {2}

Enchant player
At the beginning of each end step, create X 1/1 green Snake creature tokens, where X is the amount of life enchanted player lost this turn.

Engorge (As this enters, mill three cards, then exile a card from among the milled cards.)
When Bane of Sanity enters, if it engorged a creature card, target player discards two cards.

As an additional cost to cast this spell, sacrifice a creature.
All creatures get -X/-X until end of turn, where X is the sacrificed creature's power.

When Baneblade Stalker enters, proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)

Exile target creature or planeswalker and all other creatures its controller controls with the same name as that permanent. Search its controller's graveyard, hand, and library for any number of nonland cards with the same name as that permanent and exile them. Then that player shuffles.

Destroy all creatures. Exile all graveyards.

Counter target planeswalker spell.
Draw a card.

When Banished Prophet enters, you may remove a counter from a permanent you control. If you do, put a +1/+1 counter on another target creature you control.

Exile up to three target cards from graveyards. (Then exile this card. You may cast the creature later from exile.)

Gain control of target artifact or creature until end of turn. Untap it. If it's a creature, it gains haste until end of turn and up to one target creature can't block it this turn.

Lifelink
Forestcycling {1}, islandcycling {1} ({1}, Discard this card: Search your libary for a Forest or Island card, reveal it, put it into your hand, then shuffle.)

Golden age (If you cast an instant or sorcery spell, activated a nonmana ability, and attacked this turn, enter a renaissance for this game.)
Baptism by Fire deals 3 damage to target creature or planeswalker. If you're in a renaissance, Baptism by Fire deals 6 damage to that permanent instead.