msem-instigator

Flying (This creature can't be blocked except by creatures with flying or reach.)
When Blood-Tithe Harpy enters, target player loses 1 life and you gain 1 life.

Destroy target artifact or enchantment. You gain 2 life.

As a permanent you control explores an Aura, you may put it onto the battlefield attached to Inconspicuous Stowaway.
As long as Inconspicuous Stowaway is enchanted or equipped, she's a legendary 2/3 Cat Rogue named Agent C and has double strike.

Haste
Encourage ({T}: Another target creature you control gets +1/+1 until end of turn. Encourage only as a sorcery.)

Whenever you cast a cryptic spell, creatures you control get +1/+1 until end of turn. (Artifacts, enchantments, and modal spells are cryptic.)

Flying
When Zenith of Greed enters, search your library for up to two cards named Treasure Hoard and put them onto the battlefield, then shuffle.

When Explorer's Torch enters, draw a card.
Equipped creature gets +1/+1.
Equip {1}

Flying
Venerable Skyblade can't attack unless defending player controls a creature with flying.
When Venerable Skyblade enters, you may put a +1/+1 counter on target creature you control.

If you control an artifact, create three 1/1 colorless Construct artifact creature tokens. Otherwise, create one of those tokens.

Haste
When Volt Vermin enters, it deals damage to target player or planeswalker equal to the number of creatures with flash and/or haste you control.

Reach (This creature can block creatures with flying.)

Target creature you control deals damage equal to its power to target creature or planeswalker you don't control.
Compose (Then if you cast this from your hand, exile it and create a Saga token with “r3—You may cast a copy of this card from exile without paying its mana cost.”)

({T}: Add {R}.)
Bloodriver enters tapped.
When Bloodriver enters, target creature you control gains haste until end of turn.

Choose one or both —
• Prevent all combat damage that would be dealt to creatures this turn.
• Detain target creature. (Until your next turn, that creature can't attack or block and its activated abilities can't be activated.)

Flying
{2/U}{2/U}: Exile Aeriform Remnant. Return it to the battlefield under its owner's control at the beginning of the next end step.

{R}, Discard a card: Target creature blocking Scaled Mindreaver gains winnow until end of turn. (Damage dealt to it also causes its controller to lose that much life.)

({T}: Add {R} or {G}.)
Glittering Grove enters tapped.
Cycling {2} ({2}, Discard this card: Draw a card.)

Whenever an opponent activates an ability that isn't a mana ability, amass Soldiers 1 unless its controller pays {2}. (To amass Soldiers 1, put a +1/+1 counter on an Army you control. It's also a Soldier. If you don't control one, create a 0/0 black Soldier Army creature token first.)

Tears of Samang deals 3 damage to each creature and each player. If an opponent would be dealt damage this way, you may have Tears of Samang deal 3 damage to a planeswalker they control instead.

Enchant creature you control
When Erebos's Benefaction enters, scry 2.
Enchanted creature gets +2/+2 and has menace.

Equipped creature gets +2/+2 and protection from black and from red.
Whenever equipped creature deals combat damage to a player, that player loses 3 life unless they discard a card or sacrifice a nonland permanent. You discard a card, then you draw two cards.
Equip {2}

{T}: Add {C}.
{2}, {T}, Sacrifice Lotus Barrens: Destroy target nonbasic land an opponent controls. You and that land's controller each create a colorless land token named Lotus Spring with “{T}: Add one mana of any color.”

{T}: Add {W} or {U}.
{T}, Sacrifice Sigil of Duty: Add {W}{U}.

{T}, Tap two other untapped creatures you control: Add two mana of any one color.

Enchant creature
Enchanted creature can't attack or block.
Enchanted creature can't be the target of spells or abilities your opponents control.