Rykros is the fourth planet of the Algo star system. The planet remains hidden for most of its 1000-year, highly elliptical orbit.
Phantasy Star Portable 2"The site of the final battle of the Seed Crisis three years ago. Called the "dark planet," it was the source of the Seed plague.
Originally constructed by the Ancients as a space fortress and the ultimate weapon against the Seed, it was corrupted by Dark Falz and had become a nest that produced never-ending waves o Seed.
The four confinement systems activated during the Unification Point three years ago sealed away Rykros along with Dark Falz"
Rykros had returned in Phantasy Star Portable 2, sealed away by the Gurhal community, but returned through sub-space for the reason that the codex laid in the ruins that Shizuru Shu, while possessed by Kumhan, was hunting for.