msem-instigator

Flying
Belmord can't block.
{1}{B}: Create a 1/1 black Bat creature token with flying and “This creature can't block.” Activate only if a player gained or lost life this turn and only once each turn.

If a triggered ability of equipped creature would trigger, it triggers an additional time.
Equip {2}

First strike
Whenever Creed, Eternal Straggler attacks, exile the top card of your library. You may play that card this turn, and that spell costs {2} less to cast.

Flourishing Mountain enters tapped.
As Flourishing Mountain enters, choose a basic land type.
Flourishing Mountain is the chosen type in addition to its other types.

When Helmsman's Chart enters, draw a card.
{T}: Until end of turn, target land you control becomes the basic land type of your choice in addition to its other types.

At the beginning of your upkeep, if an opponent has more life than you, create a 4/4 red Elemental creature token with haste and “Creatures blocking this creature have winnow.” (Damage dealt to a creature with winnow causes its controller to lose that much life.)

Whenever Polgek Songcrafter attacks, other attacking creatures you control get +1/+0 until end of turn. If you control five or more attacking creatures, choose up to one target creature the defending player controls. That creature can't block this turn.

Harmony — Creatures you control gain double strike until end of turn.
When Twirling Duet enters, harmonize. (Trigger up to one harmony of one permanent you control.)

This spell can't be countered.
Protection from blue and from black (This creature can't be blocked, targeted, dealt damage, enchanted, or equipped by anything blue or black.)

Deathtouch
Other creatures you control get -1/-1.
Whenever Mother Night attacks, put target creature card from a graveyard onto the battlefield under your control.

Each player sacrifices a creature.
Reconstruct {5}{B}{B}{B} (You may cast this from your graveyard for its reconstruct cost reduced by the mana value of a permanent you sacrifice as you cast it this way. Then exile this.)

Enchant creature
When Rotten Retinue enters, return target creature card from your graveyard to your hand.
Enchanted creature gets +2/+2 and has deathtouch.

As an additional cost to cast this spell, sacrifice any number of creatures.
Target player loses 2 life for each creature sacrificed to cast Blood Lashing.

Flying
Vanishing 3 (This creature enters with three time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)

Arsenal Curator gets +1/+1 as long as you control a Plains.
{2}{W}: Untap target creature you control. It gets +0/+1 until end of turn.

Menace, haste
As long as Arleigh, Spellblade Prodigy is tapped, the first spell you cast during each other player's turn costs {U/R} less to cast. This effect reduces only the amount of colored mana you pay. (For example, if you cast a spell with mana cost {1}{R}, it costs {1} to cast.)

Abandoned Cairn enters tapped if you control another nonbasic land.
{T}: Add {B} or {R}.

Enchant creature
Enchanted creature has experience. (Whenever it attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)

Surveil 2, then create a tapped X/X green Mutant creature token, where X is the number of card types among cards in your graveyard.

Create two 1/1 white Human creature tokens.

At the beginning of your upkeep, you gain 1 life.
Whenever one or more creatures attack you, you gain 1 life.

Swiftwater Cliffs enters tapped.
When Swiftwater Cliffs enters, you gain 1 life.
{T}: Add {U} or {R}.

Other creatures you control get +0/+1.
{T}: Add {G}.

Trample
Other Hounds you control get +1/+1 and have trample.

Flying
Whenever you aetherize, you may have Telarine Skychaser become an artifact creature until end of turn.
Crew 3 (Tap any number of creatures you control with total power 3 or greater: This Vehicle becomes an artifact creature until end of turn.)