Arvad, Weatherlight Smuggler

Deathtouch, lifelink
At the beginning of your end step, if a creature died this turn, Arvad, Weatherlight Smuggler perpetually gets +X/+X where X is the number of creatures that died this turn. This ability also triggers if Arvad is in your graveyard.

Hex, Kellan's Companion

Haste
Whenever you cast an Adventure spell, if Hex, Kellan's Companion is on the battlefield or in exile, it perpetually gets +1/+1. Then if it's on the battlefield, exile it with a fetch counter on it.
Whenever you cast a spell from exile, if Hex is in exile with a fetch counter on it, put it onto the battlefield.

Reezug, the Bonecobbler

{T}: Target creature card in your graveyard perpetually becomes an artifact. You may cast that card this turn. (It loses all other card types.)

Indris, the Hydrostatic Surge

When Indris, the Hydrostatic Surge enters, conjure a card named Lightning Bolt into your library. It perpetually gains storm. Then shuffle.
Whenever you cast an instant or sorcery spell, draw a card.

Ethrimik, Imagined Fiend

When Ethrimik enters, manifest dread.
Other creatures you control get +1/+1.
As long as you control another creature, Ethrimik can't attack or block.

Mitotic Ultimus

This spell costs {X} less to cast, where X is the greatest power among creatures you control.
Trample
When Mitotic Ultimus dies, conjure two cards named Mitotic Slime onto the battlefield.

Tiana, Angelic Mechanic

Flying
When Tiana, Angelic Mechanic or another legendary creature you control crews a Vehicle, that Vehicle perpetually gets +1/+0.

Niambi, Beloved Protector

Flash
When Niambi, Beloved Protector enters, if you cast it, choose target nonlegendary creature card in your graveyard that was put there from the battlefield this turn. Return it to the battlefield. It perpetually gains "Whenever this creature becomes the target of a spell or ability, draw a card. This ability triggers only once each turn."

Jarsyl, Dark Age Scion

Starting intensity 1
At the beginning of combat on your turn, you may cast a spell with mana value equal to Jarsyl, Dark Age Scion's intensity from your graveyard without paying its mana cost. If you do, Jarsyl intensifies by 1.

Kari Zev, Crew of Two

Menace, Haste
Whenever Kari Zev attacks while you don't control a legendary Monkey, conjure a card named Ragavan, Nimble Pilferer onto the battlefield tapped and attacking. At the beginning of the next end step, if that card is on the battlefield, return it to its owner's hand.

Rusko, Clockmaker

When Rusko, Clockmaker enters the battlefield, conjure a card named Midnight Clock onto the battlefield.
Whenever you cast a noncreature spell, put an hour counter on each permanent you control named Midnight Clock. Each opponent loses 1 life and you gain 1 life.

Rothga, Bonded Engulfer

Trample
When Rothga, Bonded Engulfer enters, you get a one-time boon with "When you cast a creature spell, it perpetually gets +X/+X, where X is its power."

Ghalma the Shaper

Vigilance
Whenever Ghalma the Shaper attacks, conjure a card named Tempered Steel into your hand, then create a 1/1 colorless Myr artifact creature token.

Sala, Deck Boss

Each creature you control with an exhaust ability has haste.
Whenever you activate an exhaust ability that isn't a mana ability, copy it. You may choose new targets for the copy.

High Marshal Arguel

When High Marshal Arguel dies, conjure a card named Arguel's Blood Fast onto the battlefield and you may transform it. If you control an enchantment named Arguel's Blood Fast and a land named Temple of Aclazotz, instead create two 4/3 white and black Vampire Demon creature tokens with flying.

Vladimir and Godfrey

Rejuvenation — {2}{W}: Return Vladimir and Godfrey from your graveyard to the battlefield tapped. It perpetually gets +1/+1. Activate only if you control a 1/1 creature.

Minthara of the Absolute

Starting intensity 0
Creatures you control get +X/+0, where X is Minthara of the Absolute's intensity.
Whenever one or more permanents you control leave the battlefield, cards you own named Minthara of the Absolute intensify by 1. This ability triggers only once each turn.

Tsagan, Raider Warlord

Double strike
Start your engines!
Whenever Tsagan attacks, creatures you control get +1/+0 until end of turn for each creature you control with first strike or double strike.
Max speed — Tsagan has deathtouch. Other creatures you control have first strike.

Wild Goose Chase

Draw two cards, then discard two cards. Create a Food token.

Albiorix, Goose Tyrant

Flying, Trample, Ward {1}
Whenever you sacrifice a token, Albiorix perpetually gets +1/+1. This ability also triggers if Albiorix is in exile.

Albiorix, Goose Tyrant // Wild Goose Chase

Rankle, Pitiless Trickster

Flying
Rankle has lifelink and haste as long as an opponent controls no creatures.
When Rankle enters, you may pay 1 life. When you do, each player discards a card and sacrifices a creature.
Whenever a player discards a card, Rankle perpetually gets +1/+0.

Arek, False Goldwarden

Starting intensity 0
Whenever another creature enters under your control, cards you own named Arek, False Goldwarden intensify by 1.
{3}{W}{B}, {T}, Sacrifice Arek, False Goldwarden: Target opponent loses X life and you gain X life, where X is Arek's intensity.

Calim, Djinn Emperor

Flying, ward {2}
Calim's Breath — {1}{U}, Discard Calim: Tap up to one target nonland permanent. Draw a card. Then you may exile two other cards named Calim, Djinn Emperor from your graveyard. When you do, return Calim from your graveyard to the battlefield tapped.
When you discard Calim, conjure a card named Calim, Djinn Emperor into your library seventh from the top.

Furgul, Quag Nurturer

At the beginning of your end step, conjure a card named Slimy Dualleech onto the battlefield if you control no Leeches. Otherwise, put a +1/+1 counter on each Leech you control.
{T}, Sacrifice a creature: Add an amount of {G} equal to the sacrificed creature's power.

Euru, Acorn Scrounger

When Euru, Acorn Scrounger enters, you may forage. When you do, conjure a card named Chitterspitter onto the battlefield.
Whenever one or more Squirrels you control deal combat damage to a player, you may sacrifice a token. If you do, put an acorn counter on each permanent you control named Chitterspitter.