The roles of and within the PhD council are specified in the statutes of the PhD council (ratified via electronic vote on May 30 2018).
In addition to the PhD student council, there is also the local PhD student ombudsman:
Local CSE PhD student Ombudsman
The local CSE PhD student ombudsman is a confidential contact for PhD students in the department. The ombudsman is themselves a PhD student. You can contact them about problems you may face in your PhD studies, and the ombudsman can represent your interests and act as a mediator to supervisors/examiners.