Metamorfosis otorga un coste alternativo a una carta, así que pondrás el hechizo en la pila normalmente, pero bocaabajo, podrá ser contrarrestado por cualquier contrahechizo, y su CMC será 0 (al no tener coste de maná). Así, por
spell burst deberás pagar U simplemente. Stifle no lo contrarresaría ya que es un hechizo, no una habilidad.
Dar la vuelta a una carta con metamorfosis es una acción especial que puedes realizar en cualquier momento que tengas prioridad (incluso con un
sudden shock en la pila, ya que no es una habilidad activada). Por lo tanto ni se pone en la pila, ni tu oponente puede responderte a darle la vuelta a la carta. Podrás stiflear una habilidad que se dispare cuando se de la vuelta, pero no el hecho de darse la vuelta, que repito no es una habilidad activada ni disparada.
702.34. Morph
702.34a Morph is a static ability that functions in any zone from which you could play the card it’s
on, and the morph effect works any time the card is face down. “Morph [cost]” means “You
may cast this card as a 2/2 face-down creature, with no text, no name, no subtypes, no expansion
symbol, and no mana cost by paying {3} rather than paying its mana cost.” (See rule 707,
“Face-Down Spells and Permanents.”)
702.34b To cast a card using its morph ability, turn it face down. It becomes a 2/2 face-down
creature card, with no text, no name, no subtypes, no expansion symbol, and no mana cost. Any
effects or prohibitions that would apply to casting a card with these characteristics (and not the
face-up card’s characteristics) are applied to casting this card. These values are the copiable
values of that object’s characteristics. (See rule 612, “Interaction of Continuous Effects,” and
rule 706, “Copying Objects.”) Put it onto the stack (as a face-down spell with the same
characteristics), and pay {3} rather than pay its mana cost. This follows the rules for paying
alternative costs. You can use morph to cast a card from any zone from which you could
normally play it. When the spell resolves, it enters the battlefield with the same characteristics
the spell had. The morph effect applies to the face-down object wherever it is, and it ends when
the permanent is turned face up.
702.34c You can’t cast a card face down if it doesn’t have morph.
702.34d If you have priority, you may turn a face-down permanent you control face up. This is a
special action; it doesn’t use the stack (see rule 114). To do this, show all players what the
permanent’s morph cost would be if it were face up, pay that cost, then turn the permanent face
up. (If the permanent wouldn’t have a morph cost if it were face up, it can’t be turned face up
this way.) The morph effect on it ends, and it regains its normal characteristics. Any abilities
relating to the permanent entering the battlefield don’t trigger when it’s turned face up and don’t
have any effect, because the permanent has already entered the battlefield.
702.34e See rule 707, “Face-Down Spells and Permanents,” for more information on how to cast
cards with morph.
