msem-instigator

Whenever you cast a spell that doesn't share a color with Feathered Warden, you may gain 1 life.

Return target spell or creature to its owner's hand. If you controlled that spell or creature, catalyze. (The next spell you cast this turn costs {1} less to cast.)

Feed to the Pigs deals X damage to any target. You gain X life.

Whenever an attacking creature dies, you may pay {R}. If you do, create a 2/1 red Merfolk creature token.

Destroy target artifact or tapped land.

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.

Whenever Fickle Feeder blocks, fateseal 1. (To fateseal 1, look at the top card of an opponent's library, then you may put it on the bottom of that player's library.)

Whenever you cast a spell from your hand, exile the bottom card of your library. You may cast that card. If you don't, Fight or Fade deals 1 damage to each player.

Enchant artifact
Enchanted artifact is an Equipment and has “Equipped creature gets +2/+0” and equip {0}.

Whenever Fireheart Centaur attacks, you may pay {2}{R}. If you do, it gets +1/+0 until end of turn for each Centaur you control.

Secretly choose a creature card name. Target opponent chooses a creature you don't control. Firing Blind deals 5 damage to that creature. Reveal the chosen name, then if that creature has the chosen name, Firing Blind deals 3 damage to that opponent.

Destroy target creature. You may remove a counter from up to one target permanent.

Primal {1}{U} (During your turn, you may cast this spell for {1}{U} instead of playing a land.)
Draw two cards.

Flameblade deals 4 damage to target player or planeswalker.

Whenever a creature you control becomes tapped, exile the bottom card of your library. You may put it on top of your library. If you don't, Flames of the Forge deals 1 damage to target opponent or planeswalker.

Up to one target creature gains winnow until end of turn if you've cast another spell this turn. (Damage dealt to it also causes its controller to lose that much life.)
Flare Extensions deals 3 damage to any target.

At the beginning of your upkeep, gain control of up to one target noncreature, nonland permanent for as long as you control Flawless Heist. Then if you control five or more permanents you don't own, you win the game.

(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.”

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

Each player puts the bottom five cards of their library into their graveyard.
Fuse (You may cast one or both halves of this card from your hand.)

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

Prevent all combat damage that would be dealt this turn.

{1}{U}, {T}: Draw a card, then discard a card. You get a glory counter. (You lose glory counters before life. A player with ten or more glory counters wins the game.)
{U}, {T}: Draw a card. Only activate this ability if you are glorious.

Counter target monocolored spell.