Barn does not appear on his own, but accompanies Pasht on occasion. She quite abuses his good graces, but he remains in her thrall, simply glad to be alongside her. Pasht constantly has him carry her shopping bags and the like. This does not make him a pushover; he often intervenes to save Pasht from her own self-destructive behaviour.
He looks a middle-aged man but is older than he appears, thanks to regular doses of vampiric blood to bind him to his master's domination. If he does not drink fresh vampiric blood at certain intervals, his human age will show, and by now that means "natural" death for him. Ergo, if Pasht dies, he will follow her before long.