msem-instigator

The next time target creature would be dealt damage this turn, prevent all but 1 of that damage. Whenever that creature perseveres this turn, put a +1/+1 counter on it. (A creature perseveres when it survives damage.)

Flying
When Hallowed Perspective enters, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)
You may exert Hallowed Perspective as it attacks. When you do, until your next turn, you may cast spells as though they had flash. (An exerted creature won't untap during your next untap step.)

Flying
When Ascetic of the Folded Fan 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.”)
Each creature you control with a +1/+1 counter on it has vigilance.

Hiroto's Refuge enters tapped.
When Hiroto's Refuge enters, you may mill two cards.
{T}: Add {G} or {W}.

As an additional cost to cast this spell, return a creature you control to its owner's hand.
You may put a creature card with mana value less than or equal to the returned creature's mana value from your hand onto the battlefield with a +1/+1 counter on it.

Transcend (Activate as a sorcery to gain the next type and a +1/+1 counter.)
The first instant or sorcery spell you cast on each of your turns costs {U/R} (or {1}) less to cast.
{U}{R}: Angel — Put a flying counter and a prowess counter on Rahstahde.
{5}{U}{R}: Elder — Exile any number of instant and/or sorcery cards from your graveyard. For each card exiled this way, copy it. You may cast the copies without paying their mana costs.

Gloaming Smokeweaver has deathtouch as long as there is a creature card in your graveyard.

When Long Journey enters, exile target creature or planeswalker an opponent controls until Long Journey leaves the battlefield.

During your turn, Helene is a 4/4 Human Warrior creature with hexproof and trample that's still a planeswalker. Prevent all damage that would be dealt to her during your turn.
[+1]: Create a green Stance enchantment token with “When a creature you control deals combat damage to an opponent, sacrifice this. If you do, draw a card.”
[–2]: Create a blue Stance enchantment token with “When an opponent casts a noncreature spell, sacrifice this. If you do, counter that spell.”

When Patient Herbology enters, rouse 2. (Distribute two +1/+1 counters among permanents you control. If they aren't creatures, tap them and they become 0/0 creatures in addition to their other types.)
Sacrifice Patient Herbology: Untap target land. You gain 2 life.

Exile all cards from your graveyard. You may search your library for any number of instant and/or sorcery cards with different names that share a name with one or more cards exiled this way and cast them without paying their mana costs, then shuffle. Exile Infuse the Apparatus.

You may pay {0} rather than pay the glitch cost for spells you cast.
Whenever you cast a glitched spell, Warped Glitchmage deals 1 damage to target opponent.

Target creature you control gets +1/+2 until end of turn. If that creature is white, create a white Aura enchantment token with enchant creature and “Enchanted creature has first strike” attached to that creature.

When The Raven Queen of Fretport enters, put a -1/-1 counter on each of any number of target creatures.
{2}{U}{B}: Proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)

Tap X untapped Shamans you control: Ravik, Still-Smoke Seer deals X damage to any target and you gain X life.

Enchant creature
Concord — When Coral Guidance enters, if there are four or more card types among permanents you control, draw a card.
Enchanted creature doesn't untap during its controller's untap step.

Whenever you gain life, you may put target creature or planeswalker card from your graveyard on top of your library.

{T}: Kanaan Wardriver deals 1 damage to target creature you control. That creature gains haste until end of turn.

Flash
Enchant creature
As Legacy of Northrime enters, choose a creature type.
Enchanted creature gets +1/+4 and is the chosen type in addition to its other types.

Prevent all combat damage that would be dealt to attacking creatures you control.

Augmented — When you cast If Memory Serves, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, copy it twice. You may choose new targets for the copies.
Return target permanent card with mana value 3 or less from your graveyard to the battlefield. Exile If Memory Serves.

Bulwark — If you control a creature with toughness 4 or greater, each creature you control assigns combat damage equal to its toughness rather than its power this turn.
Creatures you control get +0/+2 until end of turn.

Create two 1/1 white Soldier creature tokens. Prevent all damage that would be dealt to them this turn.

{1}{B}: Regenerate Brainless Ghoul. (The next time this creature would be destroyed this turn, it isn't. Instead tap it, remove all damage from it, and remove it from combat.)

{1}{R}{G}: Feral Exemplar gets +2/+2 until end of turn. Activate only once each turn.
Ferocious — Whenever a creature you control with power 4 or greater attacks, that creature gets +X/+X until end of turn, where X is its power.