Requirement: 2 Advances in Medicae (Specialisation)

Your medical training allows you to find faults in anatomy and exploit them with ease. As an Action, you can break the bone of a Restrained target that you have the relevant Medicae Specialisation for. Select a Hit Location. That Hit Location now has a Broken Bone (Minor) (page 216). If the Hit Location already has a Broken Bone (Minor), it now has a Broken Bone (Major)(page 216).

Example: Klaudia has 2 Advances in Medicae (Aeldari) and is Grappling (page 208) an Aeldari Ranger (page 347). As an Action, she uses Bone Breaker on the Restrained Aeldari Ranger and targets their Arm. The Aeldari Ranger now has a Broken Bone (Minor) on that limb, inflicting Disadvantage on any actions that use it.