An Embryo (蒼の繭 Ao no Mayu lit. "Cocoon of Azure") is an artificial construct which has the ability to become anything. It is essentially a crystallisation of the Azure that is only created from thousands of amassed souls.
When a certain number of souls are amassed, an Embryo is born. The Soul Eater has the ability to create an Embryo with the many souls it can harbor, although there seems to be a technique in creating one; the amount of souls within Gigant: Take-Mikazuchi's core were enough to also create an Embryo. An Embryo can also be a power that one harbors as Hinata Himezuru was born with the power of the Embryo and could transfer it to a Prime Field Interference Manifestation, a series of artificial humans created specifically for this purpose - they include Es and the Es-N to name a few.
Embryo's have the ability to become anything from a vampire to an entire new world. Phenomenon Intervention is a power that an Embryo can employ, being capable of observing itself as a means of changing what it can become. In the example of the Embryo created by Izanami, it was able to observe multiple possibilities within itself at once and change the memories of those within it before the Amaterasu Unit descended into it.  As a power, the wielder of an Embryo has the power of Phenomenon Intervention as well and was a core part of the T-System; this same Embryo was used by Es to create the World of Tsukuyomi, and currently resides inside it with Nobody.
- Hinata Himezuru - the Code: Embryo. Was transferred to Es and then to Nobody.
- Raquel Alucard - an Embryo given shape and form into a vampire.
- The Embryo - a self-observing space monitored by the Amaterasu Unit. Took the shape and form of a new world.