Spirespine

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.

2014-04-26

If the enchanted creature leaves the battlefield, the Aura stops being an Aura and remains on the battlefield. Control of that permanent doesn't change; you'll control the resulting enchantment creature.

2014-04-26

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.

2014-04-26

Similarly, if you cast an Aura spell with bestow targeting a creature controlled by another player, and that creature is an illegal target when the spell tries to resolve, it will finish resolving as an enchantment creature spell. It will enter the battlefield under your control.

2014-04-26