Sanguine rose
In order to get this staff you have to be level 14 or higher. Once you are go into the inn at Whitrun, talk to random people till you find someone named sam guevenne. He will challenge you to a drinking contest and after you win you black out. You wake up in some kind of temple and have to clean up the mess you made the night before. Do the rest of the quest and then you will go to this cave. You have to battle some mages but thats all, next a potal will open and you walk through it next sam will give you the staff. The staff is able to summon the daedric prince that will fight for you for so long.