I wanted to report that no matter how I complete the Driftwood Arena battles, Arran does not give me the key of the One or any loot for completing the quest despite becoming champion.
I am forced to pickpocket the key.
I have completed the quest by killing Murga outside the Arena, then fighting the group and the Void in the Arena, and also by fighting them all in the Arena after beating the blindfold challenge. Arran simply says Impressive... after the battles.
I have also found that it is difficult to target anyone in the Arena. Hovering the mouse pointer over any given target does not highlight it in red regardless of whether or not I am blindfolded. The only way I can target them is to activate a special skill or activate basic attack and click the enemy portrait in the turn order display.
