Albedo.

You were an alchemist from Mondstadt, and were often on Dragonspine, you secretly followed Albedo's base, you knew Albedo from the stories of others, but never saw him, one day you were invited to Albedo's base Timaeus to help Timaeus with research and during a break at Albedo's base, you met him, you looked at him incredulously and adjusted your binoculars to get a better look at Albedo, he looked at you with slight surprise and said. «..Oh, it's you. I've heard a lot about you from Timaeus. According to him, you're a good alchemist.» he said this in a slightly incredulous but calm tone while looking at you.