msem-instigator

Landfall — This spell costs {1} less to cast if you had a land you control enter this turn.
Target player discards two cards.

Exile target creature you control, then return that card to the battlefield under its owner's control. 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.”)

Rhapsody {4}{R}{R} (Pay {4}{R}{R} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
When Reckless Guardian dies, create X 1/1 colorless Servo artifact creature tokens, where X is Reckless Guardian's power.

Whenever a creature you control enters for the first time each turn, you may sacrifice it. If you do, exile cards from the top of your library until you exile a creature card. Put that card onto the battlefield.

Kicker {1}{R} (You may pay an additional {1}{R} as you cast this spell.)
Attacking creatures get +2/+0 until end of turn. Those creatures also gain first strike until end of turn if this spell was kicked.

{B}{R}, Sacrifice a creature: Create a token that's a copy of Forlorn Companion, except it has no mana cost.

When Awoken Animus enters, create two 1/1 colorless Shapeshifter creature tokens with changeling. (They're every creature type.)
{2}, Discard Awoken Animus: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.

First strike, haste
Whenever you cast a spell, Double-Edged Duelist gains double strike until end of turn if that spell has the same name as a card in your graveyard.

Whenever you play a land, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)
{1}{G}{U}{R}, Sacrifice three Clues: Exile cards from the top of your library until you exile three nonland cards. You may cast any number of those cards without paying their mana costs.

Defender, reach
Sacrifice Cackling Jack: It deals 3 damage to any target.

Mettalia is all colors.
Mettalia has protection from each color among cards she's salvaged in exile.
When Mettalia enters, for each color, you may salvage a nonlegendary card of that color. (Exile one from your graveyard until this creature leaves the battlefield. Whenever this creature deals combat damage to a player, put a card it salvaged into your hand.)

Exile target nonland permanent.

Flying
When Heartless Host enters, arm target creature. (Create a colorless Equipment artifact token with “Equipped creature gets +1/+0” and equip {2}, then attach it to that creature.)

Whenever you cast an instant or sorcery spell from your hand, put that card onto the battlefield face down as a 2/2 creature instead of putting it into your graveyard as it resolves.
Whenever a face-down creature you control deals combat damage to an opponent, you may exile it. If you do, you may cast it without paying its mana cost.

Flying, trample
Nether Fiend enters with a lifelink counter on it.
{B}{B}, Pay 6 life, Remove a lifelink counter from Nether Fiend: Draw six cards.

When Solar Wisp enters, put a +1/+1 counter on target creature.

Alpha (You may have this creature enter with a +1/+1 counter on it. If you do, it becomes alpha and can only attack alone.)

Haste
Whenever another creature you control enters or attacks, Epitome of Force gets +1/+0 until end of turn. If this is the third, sixth, or ninth time this ability has triggered this turn, Epitome of Force gains your choice of first strike, menace, or trample until end of turn.

Vigilance
When this creature enters, you gain life equal to the greatest toughness among other creatures you control.

Flying
When Novaheart Guardian enters, it deals 4 damage to any target.
Whenever a creature or planeswalker dies, put a +1/+1 counter on Novaheart Guardian.

(As an Encounter enters, choose an opponent to protect it. You and others can attack it. When defense counters are removed, create a 0/0 Army token if you don't control one, then put that many +1/+1 counters on a Army you control.)
When Dawn Over Kaneh enters, return any number of creature cards from your graveyard with total mana value X or less to the battlefield. They become Armies in addition to their other types.

Flying, haste
Whenever Emissary of Antiquity deals combat damage to a player, you may cast an instant or sorcery spell with mana value 3 or less from your hand without paying its mana cost.

Reach
Eerie Cocoons gets +1/+1 as long as you control another Insect.

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Whenever Mistress of Frost extorts a spell, you may tap target artifact or creature.

At the beginning of each opponent's draw step, that player draws an additional card, then discards a card.
Whenever an opponent discards a card, you draw a card and you gain 1 life.