msem-instigator

This spell can't be countered.
Whenever one or more creatures with flying attack, upgrade Guided Sniper. (Give it one of the listed counters it doesn't already have.)
• +1/+1
• Reach
• Hexproof

Trample
At the beginning of your upkeep, if your fealty to Forests is five or greater, transform Hand of the Harvest. (Each Forest you control counts towards your fealty to Forests.)

Reach
Whenever one or more creatures with flying attack, harmonize. (Trigger up to one harmony of a permanent you control.)
Harmony — Harpstring Ranger gets +2/+2 until end of turn. Untap it.

Trample

When Humored Outlaw enters, choose one —
• Put a +1/+1 counter on Humored Outlaw. (Assassins, Mercenaries, Pirates, Rogues, and Warlocks are outlaws.)
• Destroy target artifact or enchantment.

You may have Icefang Wurm assign its combat damage as though it weren't blocked.
{4}{G}{G}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)

{G}: Exile target card from a graveyard. If a creature card with flying is exiled this way, put a flying counter on Illustrious Qilin. The same is true for first strike, double strike, deathtouch, haste, hexproof, indestructible, lifelink, menace, reach, trample, and vigilance.

Whenever Inspiring Tactician or another permanent you control becomes the target of a spell or ability you don't control, amass Soldiers 1. (Put a +1/+1 counter 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.)

When Intrepid Shieldmate enters, target creature gets +1/+1 until end of turn.

Vigilance
Revive {3}{G} ({3}{G}, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

Art of war — At the beginning of your end step, if Kuryu Swordsman dealt damage to an opponent this turn, you may have Kuryu Swordsman fight target creature you don't control. (Each deals damage equal to its power to the other.)

Flash
When Leafdown Ambusher enters, create three colorless artifact tokens named Arrow. They have “{T}, Tap an untapped creature you control, Sacrifice this permanent: The tapped creature fights target creature you don't control. Activate only as a sorcery unless this permanent entered this turn.”

Encourage ({T}: Another target creature you control gets +1/+1 until end of turn. Encourage only as a sorcery.)
Whenever Leotau Rider encourages a creature, that creature gains trample until end of turn.

Trample
Lotusleaf Blade gets +1/+1 as long as you control another Warrior.

Pressure {G} (You may cast this spell for its pressure cost if there are seven or more cards in your graveyard.)
Deathtouch

Whenever another creature you control enters, you may pay {2}. If you do, judge that creature. (Honor it by putting a +1/+1 counter on it or condemn it by sacrificing it to draw a card.)

Art of war — At the beginning of your end step, if Masamori Ranger dealt damage to an opponent this turn, search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

When Master of the Glen enters, create a 2/2 green Wolf Elemental creature token.
Elementals you control have trample.

Flash
Wanderlust — When Microzoologist enters, search your library for a creature card with mana value 1. If you control four or more differently named lands, you may search for a creature card with mana value 3 or less instead. Reveal that card, put it into your hand, then shuffle.

Mossvine Lurker has trample as long as it has a +1/+1 counter on it.

When Neo-Soul Naturalist enters, exile up to one target artifact or enchantment. Its controller conjures a card named Data-Point into their hand. (It's a sorcery that costs {2} with “Draw a card.”)

Vigilance (Attacking doesn't cause this creature to tap.)
Sacrifice a Fungus, Saproling, Plant, or Insect: Put a +1/+1 counter on Ontarachie Forager.

Whenever you cast a spell from exile, Promised Seeker gets +3/+3 until end of turn.
Prophecy {G} (Once each turn, you may exile a card with prophecy as you reveal it. When you do, you may cast it for its prophecy cost as long as it's exiled.)

Trample
Art of war — At the beginning of your end step, if Raiun Bay Admiral dealt damage to an opponent this turn, put a +1/+1 counter on each other creature you control.

When Reconnaissance Expert enters, mill four cards.
When Reconnaissance Expert dies, return target noncreature permanent card from your graveyard to your hand.