Mark of Execution  

 

No, you don't give anything to Mavuin (not Mauvin) - talk to him first time, he tells you he needs you to plead his case with the Tribunal, in order to do this you must defeat a Trial. Once you have the mark, you can speak to any of the 6 Tribunals (saying Mavuin is enough), and you will be told that his case will be re-opened. You then return to Mavuin, and speak to him, and he then tells you that you will need information from Karana and Mithaniel Marr, and grant a Character Flag that allows access to the Plane of Storms and the Plane of Valor (which in turn lead to the Bastion of Thunder and the Halls of Honor where Karana and Mithaniel Marr respectively can be found).