msem-instigator

At the beginning of combat on your turn, tap Tinchor, put two +1/+1 counters on him, you draw a card, and you lose 1 life.
When Tinchor dies, put his counters on target Human you control.

{G}, {T}: Add one mana of any color. When a creature enters this turn, if that mana was spent to cast it, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

Flying
At the beginning of each combat, target opponent may give themselves a poison counter. If they don't, Tower of Sorrows gets +3/+0 until end of turn.

Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Whenever you cast an Aura spell, put two +1/+1 counters on Traveling Thespians.

{2}{B}, Sacrifice a creature: Draw a card.

When Undead Archivist enters, return target instant or sorcery card from your graveyard to your hand.
Revive {5}{U} ({5}{U}, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

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.)

{T}, Sacrifice a permanent: Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Unearthed Legion's power and toughness are each equal to the number of cards in your graveyard.
At the beginning of your upkeep, mill a card.

Unending Slime enters with X +1/+1 counters on it.
{2}{G}{G}{G}: Return Unending Slime from your graveyard to your hand.

Flying
When Unraveller of Mysteries enters, mill two cards.

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

You may have Urushi, the Ripple in the Smoke enter as a copy of any creature on the battlefield, except it's an enchantment. (It's not a creature.)

When Vagabond of the Dunes enters, each opponent discards a card.
Whenever an opponent discards a card, put a +1/+1 counter on Vagabond of the Dunes.
Surpass {5}{B} ({5}{B}: Transform this creature. This costs {1} less to activate for each counter
on it. Activate only as a sorcery.)

{3}{W}: Exile Vanishing Memory and target creature an opponent controls.

Ve'aja, the First Bloodline's power is equal to the number of Clerics you control.
Whenever another nontoken creature you control dies, you lose X life and create X 1/1 black Cleric creature tokens, where X is that creature's power.

Whenever a creature you control dies, you may pay {W}. If you do, you get a glory counter. (You lose glory counters before life. A player with ten or more glory counters wins the game.)
{2}{W}, {T}: Return target creature card from your graveyard to the battlefield. Activate this ability only if you are glorious.

Vigorbreath Scourge enters with X +1/+1 counters on it.
Whenever Vigorbreath Scourge attacks, it gets +X/+X until end of turn, where X is your devotion to green. Then if its power is 6 or greater, draw a card. (Each {G} in the mana costs of permanents you control counts toward your devotion to green.)

Defender
When Virtual Access Point enters, create a Function token with “Target player mills four cards.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Vitalhydra enters with twice X +1/+1 counters on it.
Each other creature you control enters with a number of additional +1/+1 counters on it equal to the number of +1/+1 counters on Vitalhydra.

Trample
Volcanic Terror gets +1/+1 for each land card in all graveyards and in exile.

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.

Knight spells you cast cost {1} less to cast.

Defender (This creature can't attack.)
Mirage {0} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)