The Perseus was a battleship from the video game. Some time after the start of the Cylon War, it liberated a Cylon prison facility that had been holding captives (including Galactica commander Magus) inside it for over a year.
Note
This vessel is part of a separate continuity that mixes elements from the Re-imagined Series and Original Series as well as unique material. It is not a canonical item in either series.
The ship has been incorrectly referred to in some instances as a Battlestar; the Perseus is a smaller class of Colonial vessel.