Enchantment creature

Enchantment creatures are both enchantments and creatures and therefore the rules for both apply to them.

Enchantment creatures were introduced in the Theros set, where they represent the gods themselves and their emissaries (creatures with bestow). Enchantment creatures and enchantment artifacts in the Theros block all have a unique card frame that shows the starfield of Nyx.

The Nyx frame doesn't have any rules associated with it. It's just a reminder that these creatures and artifacts are also enchantments. Other enchantments in Theros use the regular card frame.