User blog comment:GodOfNerds/Character Sheet 7/@comment-4867780-20141107055038/@comment-5265497-20141107062517

"So, basically his personal lab rat ? True friendship ! XD"

Well, it seems that he reaps only benefits from the experiments and isn't actually placed in harms way.

"he started following Sebastian blindly even moving in with him when he got his house."

Plus from Sebastions view (Dax is the only follower he can share his deepest info with and trusts him with the testing of his most secret experiments) or Dax's view (a true loyalist who follows him everywhere to any end), they both have a weird mutual friendship.