Sort of. They are something of a right hand to a necromancer, or perhaps a right and left, for those who have a primary and secondary.

[ It hurts her to not say like me. She has neither. Technically, she never had both of her cavaliers at once. She's not allowed to think about that. ]

The brawn to the necromancer's brains, essentially. I've ... had two of them. Now I am but myself. [ She's a Lyctor now. She is necromancer -- but she is not cavalier, and she is certainly no one's vengeance. Harrowhark the First is but a broken fist, a meaningless gesture. ]