Nubar Kamalian is a Gateway Prospector. He had been out 5 times, nearly killed twice.
Once he landed on one Diedre-class planet, fought his way through giant cockroaches and recovered a box of Heechee disks. He was awarded $50000.
The Gateway Corporation believed the disks are worthless by-product of industrial process but himself didn't believe so. Nobody discovered that the disks operate devices such as the one found in the Gateway Museum. He used to wear on of those disks as a medallion.
He comes to the Blue Hell bar every night at 21:00. Thom Seldridge introduces him to the Gateway protagonist if he is bought a drink, otherwise he can be met there at 21:00 any night. Nubar also asks the protagonist for a drink and challenged him to a game of Old Earth trivia. Nubar scores 7 and as he loses, he awards the protagonist with his medallion.