msem-instigator

You may have Insipid Metamorph enter as a copy of any other creature on the battlefield, except it's 1/1.

As long as you control an Island, you may cast this spell as a copy of any creature on the battlefield. (This includes casting cost.)

Flying
Nectarkin enters with a +1/+1 counter on it.
Whenever Nectarkin deals combat damage to a player, permutate. (You may remove a counter from a creature you control. If you do, put two +1/+1 counters on a different creature you control.)

You may have Omendancer enter as a copy of a creature you control or a Curse you control. (If it copies a double-faced permanent, it can't transform.)

You may cast this spell as though it had flash if you pay an additional {2} to cast it.
You may have Resourceful Impersonator enter as a copy of any creature on the battlefield.

You may have Shaper of the Formless enter as a copy of any creature on the battlefield, except it has “{2}{U}: Target face-down creature becomes a copy of this creature until end of turn. Turn that creature face up. At the beginning of the next cleanup step, turn it face down.”

You may have Snowfield Doppelganger enter as a copy of any creature on the battlefield, except it has “While a player is choosing targets as part of casting a spell, that player must choose at least one other creature that shares a name with this creature if able.”

Synchronous Battle Armor and equipped creature get +1/+1 for each artifact you control.
Whenever equipped creature attacks, tap up to three target creatures.
Reconfigure {3}{U}{U} ({3}{U}{U}: Attach to target creature you control; or unattach from a creature. Reconfigure only as a sorcery. While attached, this isn't a creature.)

You may have Undecided Mimic enter or phase in as a copy of any creature on the battlefield, except it has this ability and “{2}{U}{U}: Undecided Mimic phases out.” (Treat it and anything attached to it as though they don't exist until its controller's next turn.)

You may have Warped Physiognomist enter as a copy of any creature on the battlefield with mana value 3 or less.

Enspirit (As you cast this spell, you may exile a nonenchantment creature you control until this leaves the battlefield or fails to resolve. Reduce this spell's cost by the exiled card's mana value.)
You may have Witch of Shifting Waters enter as a copy of any creature on the battlefield, except it's an enchantment in addition to its other types.

Deathwind Survivor's power and toughness are each equal to the number of enchantments you control.
Whenever an enchantment you control enters, put a +1/+1 counter on target creature.

Menace
Evanescent Soulcatcher's power and toughness are each equal to the number of cards in exile.
{2}, Exile a card from your hand: Regenerate Evanescent Soulcatcher.

The Urchin King's power and toughness are each equal to the number of cards in all graveyards.
Sacrifice a creature: The Urchin King gains lifelink and indestructible until end of turn.

Zygos, Underworld Scourge's power and toughness are each equal to the number of cards you own in exile and in your graveyard.
Spells you cast have “As an additional cost to cast this spell, you may exile any number of cards from your graveyard. This spell costs {1} less to cast for each card exiled this way.”

Gruff Clutch enters with six +1/+1 counters on it.
{R}, Remove a +1/+1 counter from Gruff Clutch: It deals 1 damage to any target.

Flying
Synchronous Hellkite enters with a +1/+1 counter for each other artifact you control.
Sacrifice three artifacts: Return Synchronous Hellkite from your graveyard to the battlefield.

You may have Unstable Impersonator enter as a copy of any creature on the battlefield chosen at random.

WZ-18 Troublemaker enters with a +1/+1 counter on it.
When WZ-18 Troublemaker dies, put its counters on target creature you control.
{1}{R}, Exile WZ-18 Troublemaker from your graveyard: It deals 2 damage to each opponent.

Augury Hydra enters with X +1/+1 counters on it.
When Augury Hydra enters, scry Y, where Y is its power, then draw Y cards.

Trample
Avatar of the Groves enters with a +1/+1 counter on it for each land you control.
Landfall — Whenever a land you control enters, proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)

Search your library for a land card, put it onto the battlefield tapped, then shuffle.
Coalesce {5}{G}{G} (You may cast this from your graveyard for {5}{G}{G}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)
Beyond All Horizons's power and toughness are each equal to the number of lands you
control.

Trample
Colossal Greatwurm enters with five +1/+1 counters on it.
Whenever a player draws a card, put a +1/+1 counter on Colossal Greatwurm.
Remove three +1/+1 counters from Colossal Greatwurm: Create a 3/3 green Wurm creature token.

Tithe (As you cast this spell, you may tap three artifacts and/or creatures you control.)
Croakfolk Marsh-Baron enters with X +1/+1 counters on it. If its tithe was paid, it enters with twice X +1/+1 counters instead.

Hexproof
Crossworld Wanderer gets +1/+1 for each differently named land you control.