The Aegian Galaxy, also called the Andromeda Galaxy on Earth, is the dominion of Poseidon.

Known species unclude humans and Lamians. The Laestrygon lived here but were exterminated by Kronos.Beyond The Impossible #223

Known planets include:

Tyre: planet invaded by Anubis 74 years before the start of the series. (Beyond The Impossible #154)