Marrow-Friend immediately assumes the the Nameless One is a deader, and moves to take a bite off him. TNO can take a step back, or let him bite him (deals 1 damage). Letting him bite TNO leads to further conversation. TNO notices a finger hanging from his neck. Asking him about this, leads him to want to gnaw on it. TNO can stop him, and telling him to take a bite of TNO instead, but not before giving TNO the Finger-Bone first grants a ring later.
Once TNO has the finger, he can either let Marrow-Friend take a bite of him (3 damage), or not. This affects alignment, see below.
Using the Finger-Bone from the inventory rewards: