msem-instigator

When Fearless Realmwalker enters, put a +1/+1 counter on each of up to two target creatures.
Whenever Fearless Realmwalker attacks, you may pay {2}{W}. If you do, aetherize it. (To aetherize, create a token that's a copy of it, then exile that token.)

When Fearless Recruit dies, create a 1/1 white Rebel creature token.

Battalion — Whenever Fearsome Army and at least two other creatures attack, creatures you control gain menace until end of turn.

This spell can't be countered.
Ward {3}
{W}, Exile Fearsome Xenoblossom from your graveyard: You gain 4 life.

Reach
Once each turn, when a creature you control dies, you may draw a card.

When Feathered Dancer enters, up to three target creatures can't block this turn.

Whenever you draw your second card each turn, draw a card.

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

When Featherfall Ascetic enters, create a 1/1 white and blue Bird creature token with flying.
Whenever a nontoken Aura enters enchanting Featherfall Ascetic, for each other creature you control, you may create a token that's a copy of that Aura enchanting that creature.

Flying, first strike, lifelink

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

Flying
At the beginning of your upkeep, 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.”)

When Fel Alston, Halfway Queen enters, return target creature card from your graveyard to the battlefield. Then exile that creature unless Fel Alston was cast for its escape cost.
Escape—{1}{W}{U}{B}, Sacrifice two creatures. (You may cast this card from your graveyard for its escape cost.)

When Felhide Marauder enters, if you control a creature with power greater than its base power, Felhide Marauder gains haste until end of turn.

Archive 5 (As this enters, shuffle the top five cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
Whenever a permanent card is put into your graveyard from the battlefield, you may put that card on the bottom of the archived library.

[+2]: Each player can cast only one more spell until your next turn.
[–3]: Exile all other permanents, then return them to the battlefield tapped under their owner's control. Creatures can't attack you or planeswalkers you control until your next turn.
[–8]: Return all permanent cards from your graveyard to the battlefield tapped.

Enchant creature
When Feline Furor enters, it deals 2 damage to enchanted creature.
Enchanted creature gets +2/+0 and has menace.

Equipment spells you cast cost {1} less to cast.
Armed — As long as Fellor Armorsmith is equipped, equip abilities you control cost {1} less to activate.

Battalion — Whenever Fellor Bloodseeker and at least two other creatures attack, Fellor Bloodseeker gains lifelink until end of turn.

Armed — Fellor Elite has double strike as long as it's equipped.

First strike

Haste
{1}{W}: Fellor Heartstriker gains lifelink until end of turn.

When Fellor Ironborn enters, you may return target artifact card from your graveyard to the battlefield. If it's an Equipment, you may attach it to target creature you control.

Battalion — Whenever Fellor Raider and at least two other creatures attack, Fellor Raider deals 2 damage to defending player.

Trample
Whenever Fellor Razer deals combat damage to a player, that player sacrifices a land.