Before giving Boneripper to Thanquol as a gift, the Warlock Engineers made sure that their creation couldn't be turned against them in the future. Boneripper cannot charge/overrun if the charge/overrun would take him into base contact with a Skaven belonging to Clan Skryre. He can never pursue a unit containing one or more members of Clan Skryre. He can never direct any of his close combat attacks against members of Clan Skryre. Also, the template of his warpfire thrower cannot be placed so that it could hit a member of Clan Skryre.