In 2372, when The Doctor presented "The Clown," a virtual reality representation of the emotion of fear, with an ultimatum, The Clown balked, believing that he had the upper hand, and responded, "Did Napoléon give an ultimatum after Waterloo? Did Chulak of Romulus give an ultimatum after his defeat at Galorndon Core?" (VOY: "The Thaw")
This character was only mentioned in dialogue.
According to the Pocket ENT novel To Brave the Storm, Chulak was a Romulan Commander who led his ship into a suicidal attack against the Enterprise at Galorndon Core during the Earth-Romulan War in 2157.
In the videogame Star Trek Online, Chulak was a 23rd century Romulan commander who was making a deal with the Na'kuhl, who were offering him a Doomsday Machine. When the weapon went out of control, Chulak's forces were decimated, and when a Na'kuhl ship crashed into the Doomsday Machine's maw, the weapon destabilized and crashed into Galorndon Core, turning it from a Romulan base into the inhospitable place location it ultimately was known to be.