I think Arandor once had this avatar; it's a direct clue! :D
By the way, I missed something – why is the first night called "The Night Musician"? There isn't a single word about music in the description of the events; perhaps it's a hint about the killer, who is somehow connected to music... a signature, a picture, something else...
I read Hostor's version, and I'm already leaning towards his finger theory because, frankly, the explanation "Arandor is the killer because he sentenced half of the players, and Lizard is the killer because 3+2=him" sounds unconvincing. I didn't quite understand his explanation, to be honest. But the finger seems too obvious, although maybe the clues in this game will be easier to find. For example, Revan has a strange black man pointing his finger at us in the same way as Xostor, and he also has something about time in his signature, but he isn't even being considered. Maybe the flowers are an analogy for immunity