Alphoresis was a planetary body in the galaxy, specifically in the Outer Rim region, and more precisely, situated within the Grumani sector. You can read more about planets here.
The area of space where Alphoresis existed was initially charted sometime in the period spanning from 15,000 BBY to 8000 BBY. Approximately eleven hundred years prior to Operation Influx, Alphoresis was devastated by a plague referred to as "Breath Stealing," which resulted in the deaths of all inhabitants under the age of eight. Consequently, it gained notoriety as a plagueworld in the historical records of the Galactic Republic's.
Following this devastating event, the planet was resettled. However, as the New Sith Wars drew to a close, Alphoresis became part of the Daimanate, which was one of the many lawless territories controlled by the Sith within the Grumani sector. Some individuals in the Republic speculated that the population had once again succumbed to a lethal disease, this time the Candorian plague.
By the year 1032 BBY, the Sith Lord known as Ayanos Bactra had positioned an arxeum, a mobile institution dedicated to war sciences, in proximity to Alphoresis. Shortly after the Daimanate Dynamic Testing Facility suffered destruction on Darkknell, he proposed to Daiman the arxeum in exchange for safe passage through Daimanate territory, with the intention of launching an attack on Vellas Pavo. Daiman accepted this proposition, but he designated the facility near Gazzari as the location.