Ghostblade Eidolon

Unlike other Aura spells, an Aura spell with bestow isn't countered if its target is illegal as it begins to resolve. Rather, the effect making it an Aura spell ends, it loses enchant creature, it returns to being an enchantment creature spell, and it resolves and enters the battlefield as an enchantment creature.

If a permanent with bestow enters the battlefield by any method other than being cast, it will be an enchantment creature. You can't choose to pay the bestow cost and have it become an Aura.

Auras attached to a creature don't become tapped when the creature becomes tapped. Except in some rare cases, an Aura with bestow remains untapped when it becomes unattached and becomes a creature.