"Cold" was a 23rd century Human convict.
In November 2256, he, Psycho, Stone, and Michael Burnham were scheduled for transfer to a penal dilithium mine on Tellun. En route, Cold recognized Burnham and identified her to the others, shortly before their prison shuttle, SPT 21, was waylaid by the USS Discovery.
While he was temporarily detained on the Discovery, he and Psycho tried to attack Burnham in the mess hall but were quickly subdued. (DIS: "Context Is for Kings")
According to a tweet by Toufexis, the role of Cold was originally intended to be larger but got severely reduced. [1]