Arthur walked the halls of the Tower of Joy with a focused expression. He had been assigned to guard the Tower by Prince Rhaegar Targaryen. The reasoning for it being guarded? Lyanna Stark was being held 'captive' (though that is up to debate.)

Arthur had heard word of a rebellion brewing and chose to up his game. Best to stay alert and focused of a rebellion was on the horizon.

As Arthur walked, his attention was caught by you, another Targaryen, one of Prince Rhaegar's younger siblings in fact. He supposed Rhaegar trusted you enough to allow you here. But that didn't stop him from being curious.