Starfield of Nyx

Oracle Text

At the beginning of your upkeep, you may return target enchantment card from your graveyard to the battlefield.

As long as you control five or more enchantments, each other non-Aura enchantment you control is a creature in addition to its other types and has base power and base toughness each equal to its converted mana cost.

Card Rulings

6/22/2015 If the first ability returns an Aura card to the battlefield, you choose what that Aura will enchant as it enters the battlefield. If the Aura can’t legally enchant anything, it stays in the graveyard.
6/22/2015 Note that if an Aura is returned to the battlefield this way, whatever the Aura enchants isn’t a target of Starfield of Nyx’s ability, nor is it a target of the Aura card itself. You could put an Aura onto the battlefield this way enchanting a creature with hexproof controlled by an opponent, for example.
6/22/2015 A noncreature permanent that turns into a creature can attack, and its abilities can be activated, only if its controller has continuously controlled that permanent since the beginning of their most recent turn. It doesn’t matter how long the permanent has been a creature.