Beast's Embrace is a covenant in Bloodborne; this covenant was introduced with The Old Hunters expansion. The name is not canon and is only a placeholder, until the official name for the covenant is released.
" When its implementation failed, the 'Embrace' became forbidden, but its knowledge became a foundation of the Healing Church.
Those who swear this oath take on a ghastly form and enjoy accentuated transformation effects...becoming the very beasts they hunted. "
Those who equip the Beast's Embrace rune are transformed into a humanoid beast and behave in a feral manner.