A man was put into a medically-induced coma after a fight at a party in a warehouse left him with a broken nose and two broken eye sockets.
The victim, 31 and from Hove, is now out of his coma but remains at Royal Sussex County Hospital in Brighton.
He requires further facial surgery.
It is understood he was a guest at a 21st birthday party when the altercation occurred at The Skate Park venue in Phoenix Place, Lewes, which only opened in January.
A Sussex Police spokeswoman said: “Police are investigating an incident at a party in Lewes on Sunday (16) in which a 31-year-old Hove man was assaulted, suffering serious facial injuries.
“He was taken to the Royal Sussex County Hospital, Brighton, where he has been detained for treatment.
“The incident happened at around 4.30am at The Skate Park, a warehouse premises in Phoenix Place, Lewes.
“A 22-year-old Lewes man was arrested on suspicion of assault causing grievous bodily harm and following interview was released on bail until 9 May while enquiries continue.”
Anyone who saw what happened is asked to phone Sussex Police on 101 or email email@example.com, quoting serial 261 of 16/3. Alternatively they can contact the independent charity Crimestoppers anonymously on 0800 555 111.