Ghen, Arcanum Weaver

Text:

, , Sacrifice an enchantment: Return target enchantment card from your graveyard to the battlefield.

Rulings:

• 11/10/2020 Because targets are chosen before costs are paid (such as the cost of sacrificing an enchantment), Ghen’s ability can’t target the enchantment you intend to sacrifice to activate its ability.
• 11/10/2020 An Aura put onto the battlefield this way doesn’t target anything (so it could be attached to an opponent’s permanent with hexproof, for example), but the Aura’s enchant ability restricts what it can be attached to. If the Aura can’t legally be attached to anything, it remains in your graveyard.