Sacrifice a creature: Add {C}{C}.

You may have Auton Soldier enter the battlefield as a copy of any creature on the battlefield, except it isn't legendary, is an artifact in addition to its other types, and has myriad. (Whenever it attacks, for each opponent other than defending player, you may put a token that's a copy of this creature onto the battlefield tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)

Flash (You may cast this spell any time you could cast an instant.)

When Breaching Hippocamp enters the battlefield, untap another target creature you control.

Flying

Feeder Mandibles -- When Canoptek Scarab Swarm enters the battlefield, exile target player's graveyard. For each artifact or land card exiled this way, create a 1/1 colorless Insect artifact creature token with flying.

{T}: Add {C}.

{U/R}, {T}: Add {U}{U}, {U}{R}, or {R}{R}.

When Contagion Engine enters the battlefield, put a -1/-1 counter on each creature target player controls.

{4}, {T}: Proliferate, then proliferate again. (Choose any number of permanents and/or players, then give each another counter of each kind already there. Then do it again.)

Flash

Drag Below -- When Dragon Turtle enters the battlefield, tap it and up to one target creature an opponent controls. They don't untap during their controllers' next untap steps.

Enthralling Performance -- When Firbolg Flutist enters the battlefield, gain control of target creature you don't control until end of turn. Untap it. It gains haste and myriad until end of turn. (Whenever it attacks, for each opponent other than defending player, you may create a token that's a copy of that creature that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)

You may have Glasspool Mimic enter the battlefield as a copy of a creature you control, except it's a Shapeshifter Rogue in addition to its other types.

Glasspool Shore enters the battlefield tapped.

{T}: Add {U}.

Flying

When Gleaming Geardrake enters the battlefield, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Whenever you sacrifice an artifact, put a +1/+1 counter on Gleaming Geardrake.

As an additional cost to cast this spell, sacrifice a creature.

Kazuul's Fury deals damage equal to the sacrificed creature's power to any target.

Kazuul's Cliffs enters the battlefield tapped.

{T}: Add {R}.

Flash

Flying

You may have Malleable Impostor enter the battlefield as a copy of a creature an opponent controls, except it's a Faerie Shapeshifter in addition to its other types and it has flying.

Dominate Monster -- When Mind Flayer enters the battlefield, gain control of target creature for as long as you control Mind Flayer.

Flash

When Misleading Signpost enters the battlefield during the declare attackers step, you may reselect which player or permanent target attacking creature is attacking. (It can't attack its controller or their permanents.)

{T}: Add {U}.

Flash

When Phantom Steed enters the battlefield, exile another target creature you control until Phantom Steed leaves the battlefield.

Whenever Phantom Steed attacks, create a tapped and attacking token that's a copy of the exiled card, except it's an Illusion in addition to its other types. Sacrifice that token at end of combat.

Raid -- If you attacked this turn, you may have Protean Raider enter the battlefield as a copy of any creature on the battlefield.

Kicker {5} (You may pay an additional {5} as you cast this spell.)

Create a token that's a copy of target creature. If this spell was kicked, create five of those tokens instead.

Flying

When Sower of Temptation enters the battlefield, gain control of target creature for as long as Sower of Temptation remains on the battlefield.

Equipped creature gets +1/+1 and has haste.

At the beginning of each combat, untap equipped creature.

Equipped creature has first strike as long as it's blocking or blocked by a Goblin or Orc.

Equip {2}

You may have Undercover Operative enter the battlefield as a copy of any creature on the battlefield, except it enters with a shield counter on it if you control that creature. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)

Deathtouch, lifelink

When Wurmcoil Engine dies, create a 3/3 colorless Phyrexian Wurm artifact creature token with deathtouch and a 3/3 colorless Phyrexian Wurm artifact creature token with lifelink.