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Opal Hound 1W
Enchantment (C)
When an opponent casts a creature spell, if ~ isn't a creature, ~ becomes a 2/2 Hound enchantment creature with first strike.

Veiled Mauler 2U
Enchantment (C)
When an opponent casts a spell, if ~ isn't a creature, ~ becomes a 3/4 Illusion enchantment creature.

Lurking Shadows B
Enchantment (C)
When an opponent loses life, if ~ isn't a creature, ~ becomes a 2/2 Horror enchantment creature with intimidate.

Dormant Flame R
Enchantment (C)
Whenever one or more creatures you control attack, if ~ isn't a creature, tap ~ and it becomes a 3/1 attacking Elemental enchantment creature.

Hidden Dryad 1G
Enchantment (C)
When an opponent plays a land, if ~ isn't a creature, ~ becomes a 3/1 Dryad enchantment creature with forestwalk.

Opal Legion 2WW
Enchantment (U)
When an opponent casts a creature spell, if ~ isn't a creature, put two 2/2 white Soldier enchantment creature tokens into play and ~ becomes a 2/2 Soldier enchantment creature.

Veiled Thresher 1U
Enchantment (U)
When an opponent casts a spell, if ~ isn't a creature, ~ becomes a 0/3 Illusion enchantment creature.
Whenever you cast a spell, if ~ is a creature, it gets +2/+0 until end of turn.

Lurking Specter 1B
Enchantment (U)
When an opponent discards a card, if ~ isn't a creature, ~ becomes a 2/3 Specter enchantment creature with flying.
Whenever ~ deals combat damage to a player, that player discards a card.

Dormant Thunder 2R
Enchantment (U)
When two or more creatures you control attack, if ~ isn't a creature, tap it and it becomes a 6/6 attacking Elemental enchantment creature. Sacrifice it at end of combat.

Hidden Troll 3G
Enchantment (U)
When a creature you control dies, if ~ isn't a creature, ~ becomes a 5/4 Troll enchantment creature.
G: Regenerate ~. Activate this ability only if ~ is a creature.

Opal Arbiter 2W
Enchantment (R)
Whenever a creature attacks or block alone, if ~ isn't a creature, ~ becomes a 3/5 Avatar enchantment creature.
As long as ~ is a creature, only one creature can attack each combat and only one creature can block each combat.

Veiled Döppelganger 1U
Enchantment (R)
Whenever an opponent casts a creature spell, if ~ isn't a creature, ~ becomes a copy of that creature except it's still an enchantment in addition to its other types.

Lurking Banshee 2B
Enchantment (R)
At the beginning of your upkeep, if ~ isn't a creature, target creature gets -1/-1 until end of turn. When that creature dies this turn, ~ becomes a 4/4 Spirit enchantment creature.
At the beginning of each player's upkeep, if ~ is a creature, that player sacrifices a creature.

Dormant Dragon 3RR
Enchantment (R)
When three or more creatures you control attack, if Dormant Dragon isn’t a creature, tap it and it becomes a 5/5 attacking Dragon enchantment creature with flying.
Whenever Dormant Dragon deals combat damage to a player for the first time each turn, untap it. After this phase, there is an additional combat phase.

Hidden Tanglewood G
Enchantment (R)
When you control five or more lands, if ~ isn't a creature, ~ becomes an Elemental enchantment creature with "This creature's power and toughness are each equal to the number of lands you control".