msem-instigator

Artifact creatures you control get +1/+1.
{U}{R}, Sacrifice an artifact: Create a 1/1 colorless Servo artifact creature token.

Menace
Augmented — Whenever you cast a spell, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, put a +1/+1 counter on Jaded Guardian. It loses this ability and gains “Whenever this creature attacks, defending player sacrifices two permanents.”

Equipped creature gets +2/+1.
Equip {2}

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.

Jagged Cairn enters tapped.
{T}: Add {R} or {G}.
{2}{R}{G}, {T}, Sacrifice Jagged Cairn: Draw a card.

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

When Jahan, the Third Shah enters, shuffle your hand and graveyard into your library, then draw three cards.
Monument {3}{U}{U} (You may cast this transformed from your graveyard for its monument cost. Exile it if it would leave the battlefield or not resolve.)

{1}, {T}: Tap target creature.

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

Flying, trample
At the beginning of combat on your turn, goad all creatures with power 3 or less. (Until your next turn, that creature attacks each combat if able and attacks a player other than you if able.)
Whenever a creature deals combat damage to an opponent, put a +1/+1 counter on it.

Activated abilities you activate cost {3} less to activate. This effect can't reduce the mana in that cost to less than one mana.
You may spend any number of colors of mana to activate attain abilities of permanents you control.

Activated abilities you activate cost {1} less to activate. This effect can't reduce the mana in that cost to less than one mana.
Attain {5}{U} ({5}{U}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

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.

When Jara Disciplinarian enters, each player sacrifices a creature.

Jara Favored gets +2/+2 as long as you've lost life this turn.

Trample
Other creatures you control have base power and toughness 8/8.

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.)

You gain 5 life. Then draw a card if you've lost life this turn.

Equipped creature gets +2/+0 and has “{T}, Unattach Javelin: It deals 2 damage to target creature.”
Equip {2}

Trample
Whenever a creature card is put into your graveyard from anywhere, put a +1/+1 counter on Jawbone, Ravenous Mutant.

As an additional cost to cast this spell, return a creature you control to its owner's hand or pay {2}.
Counter target spell.

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.)
{T}: The next creature spell you cast this turn has enspirit. When that creature enters, it becomes an enchantment in addition to its other types.

Menace
Inspired — Whenever Jeering Kit becomes untapped, target Fox you control gets +1/+1 until end of turn.

When Jeffery Stages the Finale enters, search your library for a legendary blue card, reveal it, put it into your hand, then shuffle.
Whenever you cast a spell with mana value 5 or greater, return up to one target nonland permanent to its owner's hand.

Once each turn, when Jeffery enters or you create an Aura token, you may create an Aura Role enchantment token named Lead Role attached to target creature you control. It's all colors and has enchant creature you control and “Enchanted creature has base power and toughness 5/5, is all creature types, and has flying, vigilance, trample, lifelink, and prowess.”
Whenever an enchanted creature you control attacks, draw a card.