Reger was a Betan who lived during the mid-23rd century. He was the father of Tula, and part of an underground that was organized in threes; Tamar was his contact, while Marplon was the third member of the cell.
In 2267, he provided a refuge at his house for a landing party from the USS Enterprise when they sought to escape the mayhem of the Festival, and later led them to a safe haven. After Landru discovered and abducted the landing party, Reger was able to slip away; he was somehow immune to absorption. Although part of the resistance, when he was confronted with an actual attempt to end Landru's rule, he recanted and attempted to betray the landing party to the lawgivers. (TOS: "The Return of the Archons")