As an additional cost to cast spells during an opponent's turn, you may pay {U} and reveal Promethean Jaxl from your hand. If you do, you get a lurk counter.
Flash
Promethean Jaxl enters tapped.
When Promethean Jaxl enters, you draw a card for each lurk counter you have, then you lose all lurk counters.

Whenever you gain life, you may create a 0/0 colorless Robot artifact creature token with X +1/+1 counters on it, where X is the amount of life you gained. Do this only once each turn.

Enchant creature
Enchanted creature gets +1/+1 and can't block.
Wander {1}{B}

This spell costs {1} less to cast for each card in exile you don't own.
Trample
When Proto-Class Behemoth enters, exile up to one target creature.

Flash
Ward {4}
When Psychedelic Serpent enters, gain control of target instant spell, sorcery spell, activated ability, or triggered ability. You may choose new targets for it.

Destroy target creature an opponent controls. Each other creature that player controls gets -2/-0 until end of turn.

Target creature gets +1/+1 and gains deathtouch until end of turn. Scry 1.

Enchant creature
Enchanted creature gets -X/-X, where X is your devotion to black.

Destroy target artifact. Pull the Wires deals 2 damage to that artifact's controller.

Tap up to two target nonland permanents. They lose all abilities until your next turn.

Trample
Whenever a creature you control attacks, put a +1/+1 counter on Pulse of the Unending Rave.
When Pulse of the Unending Rave dies, put its counters on up to one target creature you control. That creature becomes a copy of Pulse of the Unending Rave.

{T}: Add {C}.
Whenever you amp it up, untap Pulsing Soundsea.

Choose one —
• Destroy target creature with flying.
• Exile target enchantment.
• Target creature you control gets +1/+1 and gains hexproof until end of turn.

If you control three or more enchantments, damage dealt by sources you control this turn can't be prevented.
Punishment from Nyx deals 2 damage to any target.

Gain control of target creature until end of turn. Untap that creature. It gains haste until end of turn.
You choose which creatures block this turn and how those creatures block.

Lifelink
Other creatures you control with lifelink get +1/+1.
If another source you control with lifelink dealing damage would cause you to gain life, you gain twice that much life instead.

When Pursuer of Divinity enters, you may search your library for a double-faced card, reveal it, put it into your hand, then shuffle.
Cybersoul {4}{W}{B}

Flying
Solidarity
Whenever Pyrewing Penancer attacks, it deals damage equal to its power to each opponent.

Flying
Whenever you cast a spell that targets a single creature you control, bless that creature.

Haste
{T}, Sacrifice Pyrote Entity: It deals 1 damage to any target.

Whenever you amp it up, Pyrote Technician deals 2 damage to each opponent.

Each creature you control gets +2/+1 as long as you control two or more other creatures with the same name as it.
{3}{C}, {T}: Create a token that's a copy of target creature you control.

Whenever you attack with exactly two creatures, draw a card. Prevent all damage that would be dealt to creatures you control this turn.

Flying, deathtouch, haste

Quantum Skycity enters tapped.
{T}: Add {W} or {U}.
{T}, Discard another card named Quantum Skycity: Draw a card.