Castellaño was a Manticoran citizen and an officer of the Landing City Police Department. Holding the rank of Lieutenant, he served as Master of the Field at the duel between Honor Harrington and Denver Summervale, as well as at the one between Harrington and Lord Pavel Young, Earl of North Hollow. During the latter one, he exercised his duty to execute the Earl for violating the rules (by shooting while Harrington's back was still turned), but Harrington's bullets had already killed Young by the time Castellaño's pulser darts shredded him to pieces. (HH4)