msem-instigator

When Horn of Seasons enters, search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
Equipped creature gets +3/+0.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Flying, prowess
Whenever you cast a noncreature spell, reveal the bottom two cards of your library. Target opponent chooses one of them. Put that card on the bottom of your library and the rest into your hand.

First strike
When Faradia's Collector enters, if an opponent controls more lands than you, create a colorless artifact token named Lotus Petal with “{T}, Sacrifice this artifact: Add one mana of any color.”

{T}: Add {C}.
At the beginning of each end step, if you control five or more Snake creatures, transform Aghavaan's Wound.

As Rhythm of Avaz enters, choose Cyrukan or Sahra.
• Cyrukan — At the beginning of combat on your turn, put a +1/+1 counter on target creature you control.
• Sahra — Creatures you control have menace and haste, and attack each combat if able.

Archive X (As this enters, shuffle the top X cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
Whenever you draw a card from the archived library, create two 1/1 green Insect creature tokens.

Flash (You may cast this spell any time you could cast an instant.)
When Stampede Instigator enters, target creature gets +2/+3 until end of turn.

Flying
When Scion of Torrents enters, you may return target nonland permanent to its owner's hand.
Whenever an Island you control enters, you may aetherize Scion of Torrents. (To aetherize, create a token that's a copy of it, then exile that token.)

Vision (Whenever this or another creature you control enters, reveal the top card of your library. Then you may put that card into your graveyard.)
Whenever Gleaming Rider envisions an instant or sorcery card, target creature becomes a 5/5 Elk Spirit until end of turn.

{1}{B}, Sacrifice another creature: Put a +1/+1 counter on Voracious Ghoul.

Heroic — Whenever you cast a spell that targets Halcyon Hoplite, Halcyon Hoplite gains flying until end of turn.
When Halcyon Hoplite dies, if it was enchanted, create a 1/1 white Bird creature token with flying.

Put a +1/+1 counter on target creature and a +1/+1 counter on up to one target Citizen or Peasant.

Whenever Loyalist Escort or another Knight or Soldier you control enters, you may choose one that hasn't been chosen this turn —
• Tap target creature an opponent controls.
• Untap target creature you control.

Harmony — Warriors you control get +1/+0 and gain menace until end of turn.
Whenever Aleud Warcaller attacks, harmonize. (Trigger up to one harmony of a permanent you control.)

Flash
Enchant player
When Curse of Ceaseless Pursuit enters, put two +1/+1 counters on target creature you control.
Creatures attacking enchanted player have trample.

Whenever a creature you control enters, create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)
{2}, Sacrifice an Idol: Creatures you control get +1/+1 until end of turn.

Vigilance, trample
{5}{R}{G}: Monstrosity 4. (If this creature isn't monstrous, put four +1/+1 counters on it and it becomes monstrous.)

Prevent all combat damage that would be dealt this turn by non-Army creatures.
Amass Soldiers 2. (Put two +1/+1 counters on an Army you control. It's also a Soldier. If you don't control one, create an 0/0 black Soldier Army creature token first.)

Cast this spell only before attackers are declared.
Target creature you control gets +X/+0 until end of turn and gains haste until end of turn, where X is its power. At the beginning of the next end step, sacrifice that creature if it attacked this turn.

Choose one or both —
• Riverboat Assault deals 3 damage to target creature.
• Target creature gets +3/+3 until end of turn.

When Journey to the Zhedina enters, draw a card, then choose a creature card name.
Whenever a creature with the chosen name you control deals damage to a player, put a +1/+1 counter on it.

Exile the top card of your library. You may play that card until the end of your next turn.

Flying

This spell costs {X} less to cast, where X is your devotion to green. (Each {G} in the mana costs of permanents you control counts toward your devotion to green.)
Trample