msem-instigator

Whenever another nontoken creature enters the battlefield under your control, create a 1/1 green Saproling creature token.
{1}{G}, {T}: Populate. (Create a token that's a copy of a creature token you control.)

Create two 1/1 red Elemental creature tokens.

When Ankulith Shard enters the battlefield, draw a card.
{1}, {T}: Add one mana of any color.

Create two 1/1 red Elemental creature tokens. When you do, target creature you control gets +X/+X and gains trample until end of turn, where X is the number of Elementals you control.

Annihilation deals X damage to any target.

When Anointed General enters the battlefield, if you control a legendary creature, Anointed General deals 4 damage to target creature you don't control.

When Anran's Radical enters the battlefield, you may discard a card. If you do, search your library for a card with mana value 5 or greater or with {X} in its mana cost, reveal it, put it into your hand, then shuffle.
{T}: Add {C}.

Anran's Realm enters the battlefield tapped.
{T}: Add {R} or {G}.
{R}{G}, {T}: Create a Function token with “This spell can't be countered.” Activate only if you control a creature with power 4 or greater. (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Reach, trample
When Anran, Root Steward enters the battlefield, destroy up to three target noncreature permanents. For each permanent destroyed this way, its controller creates a colorless enchantment land token named Paradise with hexproof and “{T}: Add one mana of any color.”

Equipped creature gets +1/+0 and has “{T}: This creature deals 1 damage to target player or planeswalker.”
Equip {2}

Antu, Sun Spirit can't attack or block unless you control ten or more permanents.
As long as it's your turn, other creatures you control get +X/+0 and have haste, where X is the amount of life you've gained this turn.
When Antu dies or is put into exile from the battlefield, you may put him into his owner's library third from the top.

Colossal 4—{8} (You may cast this for its colossal cost to have it enter with four +1/+1 counters; or pay {8} as a sorcery: Put four +1/+1 counters on it if it has none.)
Abilities you activate that aren't mana abilities cost {2} less to activate. This effect can't reduce the mana in that cost to less than one mana.

Flash
Flying

Each land is an Island in addition to its other land types.

As Aparodist enters the battlefield, choose a non-Human creature type.
Aparodist is the chosen type in addition to its other types.
{1}, {T}: Put a +1/+1 counter on each creature you control of the chosen type.

Vigilance, trample
Whenever another Horror enters the battlefield under your control, choose one —
• Destroy target artifact or enchantment.
• You gain 4 life.
• Apex Abomination fights another target creature.

At the beginning of your upkeep, if an opponent controls more creatures than you, you may reveal the top seven cards of your library. Target opponent chooses a creature card revealed this way. Put that card onto the battlefield, and the rest into your graveyard.

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 “III—You may cast a copy of this card from exile without paying its mana cost.”)

Whenever Apprehensive ‘Slinger deals combat damage to a player or planeswalker, you may discard a card. If you do, draw a card.

When Apprentice Summoner enters the battlefield, search your library for a creature card with mana value 1 or less, put it onto the battlefield, then shuffle.

When Appropriated Gear enters the battlefield, create a Treasure token.
Equipped creature gets +1/+1.
Equip {2}

Other creatures you control can't attack or block alone.

{1}{R}: Aravant Throatcutter and up to one other target Pirate or Rogue you control each get +1/+0 until end of turn.

Target creature you control deals damage equal to its power to target creature you don't control.

This spell costs {1} less to cast for each differently named land you control.
Reach, trample