He comes back bearing the blindfold and attaches it to Carissa, and then sits there, breathing deeply.
He cuts his forearm with the illusionary knife, just to make sure the blade isn't real. It hurts like a real cut (and will for ten minutes supposedly), the skin is unbroken, there's no blood.
Abrogail literally tortured Carissa to death and subjected her to worst fear, and Carissa came back visibly brighter and happier, and maybe even persistently better though it's hard to tell; and if that maybe required some skill that Keltham doesn't have, and wouldn't work for everyone or on anyone, it at least illustrates that he really really is not in dath ilan anymore. Adaptation is a virtue, one should not go on living in a world that no longer holds you.