msem-instigator

Frontier Base enters tapped unless you have 15 or less life.
{T}: Add {G} or {U}.

Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
Whenever you cast a spell during an opponent's turn, tap target nonland permanent.

Whenever a spell or ability with one or more targets is put onto the stack, reselect its targets at random.

Basic Forests you control have “{G}, {T}: Untap target attacking creature and remove it from combat.”

When Grisly Reaper enters, you may exile a creature card from your graveyard. When you do, create a 1/1 black Skeleton creature token.

When Wayfaring Swindler enters, destroy all permanents attached to target creature.

Nameless Throng can't block.
{1}{B}, Exile an artifact or enchantment card from your graveyard: Return Nameless Throng from your graveyard to the battlefield.

When Sword of the Heavens enters, attach it to target creature you control.
Equipped creature gets +2/+2 and has flying, vigilance, and “Whenever this creature attacks, you may search your library and/or graveyard for an Aura or Equipment card, reveal it, put it into your hand, then shuffle.”
Equip {3}

{T}: Add {G}.

Search your library for two basic land cards and put them onto the battlefield tapped. Then they become 0/1 green Plant creatures with “This creature can't block” in addition to their other colors, types, and abilities.

Caustic Mangrove enters tapped.
{T}: Add {B} or {G}.
{1}, {T}: Add one mana of any color.

When Abberant Frostbringer enters, tap up to one target creature. If you do, put two stun counters on that creature. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Other Merfolk you control get +1/+1.
{1}{U}: Target Merfolk gains slipstream until end of turn. (Creatures with slipstream can't be blocked as long as only creatures with slipstream are attacking.)

Trample, haste

At the beginning of your upkeep, if Blade of Ancestors isn't attached to a creature, create a 1/1 white Soldier creature token, then attach Blade of Ancestors to it.
Equipped creature gets +1/+1.
Equip {2}

When Batiga Escort enters, create a 1/1 blue Bird creature token with flying.
{2}{W}, {T}: Put a +1/+1 counter on each creature you control with flying.

Monstrous Amalgam gets +X/+X, where X is the number of creature cards in your graveyard.
{B}, Reappropriate: Put a +1/+1 counter on Monstrous Amalgam. Activate only once each turn. (To reappropriate, exile exactly two cards from your hand and/or graveyard.)

Counter target spell.
Look at the top three cards of your library. Put one on top and the rest on the bottom in any order.

Vigilance
{3}{G}, {T}: Target creature you control fights target creature you don't control.

When Fateshifter's Prophet enters, you gain 2 life and scry 2.

Flying
Whenever AOSE Skydrone deals combat damage to a player, draw a card.

This spell costs {1} less to cast for each creature you control that attacked this turn.
First strike
Whenever Weavetide Militia and at least one other creature attack, creatures you control get +1/+0 until end of turn.

Flying
Whenever you cast a multicolored spell, create a 3/3 white Angel creature token with flying.

Target player sacrifices an attacking or blocking creature. Prevent all damage that would be dealt by creatures this turn.

Flying
Crew 4 (Tap any number of creatures you control with total power 4 or greater: This Vehicle becomes an artifact creature until end of turn.)
Tap two untapped other artifacts you control: Encampment Blimp becomes an artifact creature until end of turn. Scry 1.