msem-instigator

Whenever Ferris, the Sapphire Storm or another creature you control enters, each opponent mills X cards, where X is that creature's power.

Whenever a permanent with one or more counters on it is put into your graveyard from the battlefield, it deals that much damage to any target and you gain that much life.

Whenever a nontoken creature you control dies, create a 1/1 black Worm creature token.
Sacrifice Fertile Grave: Create a 1/1 black Worm creature token.

Fertile Steppe enters tapped unless you have 15 or less life.
{T}: Add {G} or {W}.

{1}, {T}, Move a -1/-1 counter from another creature onto Fervent Arbiter: Exile target creature you don't control until Fervent Arbiter leaves the battlefield.

At the beginning of your upkeep, exile the top card of your library. Until end of turn, you may play that card if it's an instant or sorcery card.

Menace
When Fervent Devout enters, choose one —
• Put a +1/+1 counter on Fervent Devout.
• Create a colorless artifact token named Lotus Petal with “{T}, Sacrifice this artifact: Add one mana of any color.”

Chosen one ({W}{U}{B}{R}{G}: Transform this permanent.)
Whenever Fervent Ensign attacks, add {R} at the beginning of your next main phase.

Flying
You may exert Fervent Igmel as it attacks. When you do, add {R}{R}{R}{R}. Until end of turn, you don't lose this mana as steps and phases end. (An exerted creature won't untap during your next untap step.)

Attacking creatures you control get +1/+0.

{2}{R}{R}, Exile an instant or sorcery card from your graveyard: Fervid Dragonheart gets +1/+2, gains flying, and becomes a Dragon until end of turn.

Whenever a creature you control dies, put a rot counter on Fester Swarm and you gain 1 life.
{B}{G}, Remove two or more rot counters from Fester Swarm: Create a 1/1 green Insect creature token, then put a +1/+1 counter on it for each rot counter removed this way.

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

When Festering Shipwreck enters, create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)
At the beginning of each player's upkeep, that player sacrifices a nonland permanent.

At the beginning of your upkeep, mill a card.
{1}, Exile three cards from your graveyard: Put a -1/-1 counter on target creature.

When Festering Waif enters, each opponent mills two cards.
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.)

When Festival Celebrants enters, put a +1/+1 counter on each creature you control.

Golden age (If you cast an instant or sorcery spell, activated a nonmana ability, and attacked this turn, enter a renaissance for this game.)
{T}: Add {C}. If you're in a renaissance, add one mana of any color instead.
{3}, {T}: Scry 1.

Inspired — Whenever Festival Decorator becomes untapped, draw a card.

When Festival Rioters enters, create a colorless artifact token named Lotus Petal with “{T}, Sacrifice this artifact: Add one mana of any color.”
{1}{R}: Festival Rioters gets +2/+0 until end of turn.

Harmony — Create a 1/1 white Bird creature token with flying.
{4}: Harmonize. (Trigger up to one harmony of one permanent you control.)

Enchant creature you control
When Festive Euphoria enters, you gain life and draw cards equal to enchanted creature's power.
Enchanted creature can't be blocked by creatures with power 2 or less.

Festive Servitor gets +1/+1 for each color among spells you've cast this turn.
{2}: Add one mana of any color.

When Fetching Gancanagh dies, draw a card. At the beginning of the next end step, up to one target creature you control becomes a copy of Fetching Gancanagh.

{B}: Fetid Nibbler gains deathtouch until end of turn.