Who is Colonel Morden from Clarissa and what is their importance?

Colonel Morden is the Harlowes' cousin. He has been abroad for six years, and he returns when he hears about the discord between Clarissa and the rest of the family. As trustee, Morden attempts to mediate between the family members, but he is unable to persuade the Harlowes to relent. In the end, he avenges Clarissa against Mr. Lovelace, partly to prevent James, an only son, from doing so.