msem-instigator

Whenever Arena Challenger deals damage to a creature, upgrade it. (Give it one of the listed counters it doesn't already have.)
• +1/+1
• First strike
• Prowess

Target creature you don't control fights target creature you control, then fights up to one other target creature you don't control.

Whenever Bold Vanquisher attacks, upgrade it. (Give it one of the listed counters it doesn't already have.)
• +1/+1
• Trample

Engulf in Flames deals 1 damage to target player and each of up to three target creatures that player controls. Those creatures can't block this turn.

Equipped creature gets +1/+0 and has menace.
Equip {1}

Glitch {2} (Remove one [restriction] for each time you pay the glitch cost.)
Until end of turn, target creature you control gets +3/+0 and gains first strike and haste. [Sacrifice it at the beginning of the next end step.]

Flooding Magma deals 2 damage to each creature except for equipped creatures you control.

(Add a quest counter as this enters. Sacrifice after 5.)
Whenever you cast a spell, add a quest counter.
1 — Discard a card. If you do, draw a card.
2, 3, 4 — Target opponent discards a card, then draws a card. If they discarded a card with greater mana value than each spell you control, remove a quest counter from Gambler's Tournament.
5 — Discard your hand, then draw seven cards.

Equipped creature gets +3/+1 and has haste.
Equip Soldier or Warrior {1}
Equip {4}

Glitch {2} (Remove one [restriction] for each time you pay the glitch cost.)
Improbable Aim deals damage to target creature or planeswalker equal to the number of [instant and sorcery] cards in your graveyard.

Trample
{1}{R}: Each attacking creature you control with trample gets +1/+0 until end of turn.

Double strike, menace, trample
At the beginning of your end step, sacrifice Juddering Mishap unless you've cast a spell with no creature types this turn. (Noncreature spells have no creature types.)

Whenever you cast a spell that targets one or more permanents you don't control, gain control of those permanents until end of turn. Untap them. They gain haste until end of turn.

Glitch {2} (Remove one [restriction] for each time you pay the glitch cost.)
Lag Spike deals 3 damage to target [blocking] creature.

When Living Hoard enters the battlefield, create a Treasure token.
{R}, Sacrifice an artifact: Living Hoard gets +2/+0 until end of turn.

When Load-Bearing Behemoth dies, destroy target artifact or land.

Choose target creature, then flip a coin. If you win the flip, Long Shot deals 5 damage to that creature. Otherwise, return Long Shot to its owner's hand.

Magma Bolt deals 2 damage to any target. If a creature dealt damage this way would die this turn, exile it instead.

Glitch—Discard a card. (Remove one [restriction] for each time you pay the glitch cost.)
Add {R} for each [Mountain] land you control, then exile the top three cards of your library. You may play [one of] those cards this turn.

Glitch {2} (Remove one [restriction] for each time you pay the glitch cost.)
Create a 3/2 red creature token named Error with trample and haste. [Exile it at the beginning of the next end step.]

Target creature gets +4/+3 until end of turn. Put a trample counter on it.

Haste
Whenever Mukal Charger attacks during your first combat phase each turn, untap all Constructs you control. After this phase, there's an additional main phase followed by an additional combat phase.
Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)

Haste
Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)

As an additional cost to cast this spell, pay {3} or discard a card.
Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)

Trample
Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)