msem-instigator

Siphon (Each -1/-1 counter you put on your creatures up to their remaining toughness while casting this pays for {1}.)
Counter target spell unless its controller pays {4}.

Menace
Whenever Flayed Dunerazer attacks or blocks, sacrifice a permanent.

Breach (Whenever this deals combat damage to a player, you may have it become an Aura Curse until your next turn. Attach it to that player.)
Once each turn, when a Curse you control becomes attached to an opponent, you may sacrifice it. If you do, reveal cards from the top of your library until you reveal a Curse card. Put that card onto the battlefield attached to that player, and the rest on the bottom of your library in a random order.

Flash
This spell costs {1} less to cast for each Dragon you control.
Flying

Whenever you cast a black spell, put a +1/+1 counter on Flenser's Lieutenant.
{B}{B}: Return Flenser's Lieutenant from your graveyard to your hand.

Whenever a creature an opponent controls dies, monstrosity 1. (If this creature isn't monstrous, put a +1/+1 counter on it and it becomes monstrous.)

Vanishing 1 (This permanent enters with a time counter on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
When Flesh to Rot enters or the last time counter is removed from it, all creatures get -3/-3 until end of turn.

Deathtouch
When Flesheater Vine enters, you may have it consume. If you do, put a +1/+1 counter on it and you gain 3 life. (To consume, sacrifice another creature or exile a creature card from your graveyard.)

As an additional cost to cast this spell, exile a creature card from your graveyard.

Flying (This creature can't be blocked except by creatures with flying or reach.)
At the beginning of your upkeep, put a +1/+1 counter on Fleshrender Demon and you lose 1 life.

Whenever Fleshwarper or another Horror you control dies, each opponent loses 1 life and you gain 1 life. You may mill a card.

When Fleshwrithe Ghoul enters, each player sacrifices a creature.
Revive {4}{B} ({4}{B}, 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.)

Flash
Flying
Whenever another Spirit you control enters, put a +1/+1 counter on Flickers in the Night.

Create X 4/4 white Angel creature tokens with flying.
Flashback {X}{W}{W}{W}{W}{W} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Enchant creature
When Flight of Fancy enters, draw two cards.
Enchanted creature has flying.

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
You don't lose unspent red mana as steps and phases end.
I, II — Add {R}{R}.
III — Create a 3/3 red Phoenix creature token with flying, haste, and “{R}: This creature gets +1/+0 until end of turn.”

Lifelink
Pay 3 life: Flightful Fledgling gains flying until end of turn.

Whenever another creature you control enters, Flightpath Trainee gains flying until end of turn.

Flash
{6}: Target creature gains flying until end of turn.

Return all creatures with toughness 3 or less to their owners' hands.
Investigate three times. (To investigate, create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Flooding Magma deals 2 damage to each creature except for equipped creatures you control.

Flying
Menagerie — At the beginning of combat on your turn, if there are five or more creature types among creatures you control, create a 1/1 black Insect Spirit creature token with flying and you gain 1 life.

(Add a quest counter as this enters. Sacrifice after 3.)
At the beginning of your end step, if you have more life than an opponent, add a quest counter.
1, 2 — Mill two cards. You may put one of those cards into your hand. If you do, you lose 3 life. Otherwise, you gain 3 life.
3 — Return target creature or planeswalker card from your graveyard to the battlefield.

Trample
Heretic (Whenever you cast a spell that doesn't share a color with this creature, it gets +1/+1 until end of turn.)