Dmitri Gulov is a Russian Black Market dealer who was in Yara with his twin brother, Vasily, for a deal with Bembé Álvarez. The deal went sideways when they were waiting for Bembé at the El Tigre Dormido Hotel when the FND showed up there. His brother was murdered and he was being beaten by Castillo's men, especially Lieutenant Trius who tortured him. Dani is sent to acquire a key from him to help cover Paolo's debt. Should Dmitri survive, he'll speak of leaving Yara while warning Dani of Bembé double-crossing them. Regardless of his fate, he is never seen again after that.
Due to the dangerous nature of black market, Dimitri prepared for his death in advance, left behind his last message and the gun Iron Curtain as a gift to his brother Vasily. Unfortunately, it was Vasily who died while Dimitri survived instead, likely the reason why Dimitri left and let Dani keeps the gun.