Ashiok, urdidor de pesadillas

Ashiok's second ability doesn't target any creature card. You choose which creature card to return when that ability resolves, but you must choose one with mana value equal to the value you chose for X when activating the ability.

Ashiok's second ability refers to any creature card exiled because of Ashiok's first or third ability.

If Ashiok leaves the battlefield, and later another Ashiok enters the battlefield, it is a new object (even if the two were represented by the same card). Creature cards exiled by the original Ashiok can't be put onto the battlefield by the second ability of the new Ashiok.

If you put a creature card with bestow onto the battlefield, it will be a creature on the battlefield, not an Aura.

If you put a creature card with {X} in its mana cost onto the battlefield, the value of that X is 0.