msem-instigator

Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{3}{G}, Sacrifice Jade Vault Reclaimer: Destroy target artifact or enchantment.

As long as Jadycian Empath is on the battlefield or in your graveyard, it's a land in addition to its other types.
Sacrifice Jadycian Empath: Add one mana of any color.

({T}: Add {R} or {W}.)
Jagged Crag enters tapped.

Whenever Jak, Daring Vanguard or another legendary creature you control enters, creatures you control get +1/+0 and gain haste until end of turn.

Menace
Jara Champion can only attack or block alone.
Whenever one or more players lose life for the first time each turn, put a +1/+1 counter on Jara Champion.

Trample, haste
Cadence (Whenever you cast a spell, if its mana value is greater than this creature's power, put a +1/+1 counter on this creature.)

Bloodprice {B}{B}{B}{B} (You may cast this card by sacrificing a creature and paying its bloodprice.)
Lifelink, haste
Sacrifice another Demon: Jejun, Dark Hunter gains flying and indestructible until end of turn.

Hexproof
At the beginning of each end step, if an opponent was dealt 4 or more damage this turn, return target instant or sorcery card from your graveyard to your hand.

Each player sacrifices a creature and discards a card.
Fuse (You may cast one or both halves of this card from your hand.)

Indestructible
At the beginning of combat on your turn, you may untap target land you control. If you do, that land becomes an X/X green Beast creature with haste until end of turn, where X is the number of differently named lands you control. It's still a land.

When Jobiah, Devoted Farmer enters, search your library for a land card, put it onto the battlefield tapped, then shuffle.
At the beginning of your upkeep, if you control six or more lands with different names, you may transform Jobiah.

Choose two. You may choose the same mode twice —
• Create a 1/1 green Insect creature token.
• Put a +1/+1 counter on target creature you control.

Put target creature or planeswalker on the bottom of its owner's library. Its controller may scry 1.

As Joyous Chromatelk enters, choose a color.
All cards that aren't on the battlefield, spells, and permanents are the chosen color in addition to their other colors.
{T}: Add one mana of the chosen color.

Noncreature spells your opponents cast cost {1} more to cast for each counter on Judges of Bearidge.
{5}{W}{U}: Put a +1/+1 counter on Judges of Bearidge, then detain each creature with lesser power. (Until your next turn, those permanents can't attack or block and their activated abilities can't be activated.)

Flying
Concord — When Judicious Djinni enters, if there are four or more card types among permanents you control, return target instant or sorcery card from your graveyard to your hand.

Jungle Hollow enters tapped.
When Jungle Hollow enters, you gain 1 life.
{T}: Add {B} or {G}.

When Junktrawler enters, create a tapped colorless Powercell artifact token with “{T}: Add {C}.”
Tap another untapped artifact you control: Junktrawler gets +1/+1 until end of turn.

Flash
Flying
When Justiciar Overseer enters, the next 2 damage that a source of your choice would deal to you and/or permanents you control this turn is dealt to any target instead.

(Choose only one work as a sorcery to add its ability.)
When Juyu Offering Pool enters, reveal the top five cards of your library. You may put a noncreature card from among them into your hand. Put the rest on the bottom of your library in any order.
{1}{U}: Scales of Shara
Whenever you cast a noncreature spell, put a +1/+1 counter on target creature you control.
{6}{U}{U}: Eye of Shojiro
Whenever you cast a noncreature spell, create an 8/8 blue Kraken creature token.

Whenever an artifact you control becomes tapped, K-17 Drone deals 1 damage to each opponent.

Flying
When Kaalia's Abomination enters or dies, it deals 2 damage to target opponent. Then that player discards two cards.

Flying
When Kai'Dwo, Eternal Ravager enters, create seven Idol tokens. (They're artifacts with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)
Whenever you sacrifice an Idol, each opponent sacrifices a creature.

Flying
Ward—Discard a card.
Whenever Kai'Oro enters or attacks, you may exile target nonland card with mana value 3 or less from your graveyard. Until end of turn, you may cast a copy of that card without paying its mana cost.

Whenever a creature attacks you or a planeswalker you control, put that creature on the bottom of its owner's library unless its controller pays {2}.