As a solution to this puzzle? Then I got the other one wrong, too, I guess. I was just pretty sure, the guy trapped in the basement of the church was William Whitegate. After solving it with your help I went back to look for clues, how to figure out it was Anton. I couldn't really make the connection.

There are actually two valid sigils. Are you perhaps referring to the other one?

I was so sure, he's William Whitegate, that I spent about an hour on the wrong sigil. Where was the clue, he's Anton?