The serious assault happened after three men tried to get into a house party in the east end of Glasgow.
They tried access the flat in Meadow Park Street, Dennistoun and one of the men also tried to climb a drainpipe to get in.
When they were refused entry a fight broke out which spilled in to the close and led to a 27-year-old man suffering a “serious facial injury”.
Two other men, both 26, also received minor injuries.
They were taken by ambulance to Glasgow Royal Infirmary, where the 27-year-old is being treated.
Medical staff describe his condition as stable, but say he will have a permanent scar following the attack.
The three men made off on foot along Meadow Park Street and towards Glasgow Club Whitehall on Onslow Drive.
Two of the suspects are white, 5ft 7in, 20-30, with dark hair, dark eyes and bushy eyebrows and a local accent.
Another is white, 6ft, 20 - 30, with red/fair hair and a Glasgow accent, wearing a grey hooded top with black writing on it.
Detective Constable Sean McLoughlin, Shettleston CID, said: “This attack was as much cowardly as it was vicious and it has left a young man with a permanent scar across his face.
“The suspects had no reason to try and get into the party, it was a private house party for friends and for this to happen is just awful.”
Police believe people from a nearby pub, the La Cala Bar, may have seen the three suspects run from the flats past them after the attack.
DC McLoughlin added: “We know that the pub was spilling out at the time and there were a number of people either waiting for taxi or out for a smoke around that time.
Anyone with information is asked to call Police Scotland on 101.