"These rare Brassilisks are powered by blue soul gems brought back from the Psijic hideaway of Artaeum at the end of the First Era by Sotha Sil himself."
The Psijic Brassilisk is a pet brassilisk for The Elder Scrolls Online. It is available exclusively to PlayStation 4 players with an active PlayStation Plus account and can be purchased from the PlayStation Store for free until December 31st, 2017.
The pet was added to promote the Clockwork City DLC, but does not need the DLC to be obtained.