I looked and haven't found the official artist, which is strange because Critical Role will usually credit them. My theory is that the artist was commissioned by Ubisoft, and they paid an additional fee so the art didn't have to be credited. I could obviously be wrong, as I haven't watched the one-shot, but I don't think they were publicly credited.

Ubisoft is also generally good with crediting their artists with many of them posting their works to ArtStation so I don't know why this would be different but maybe.

Yeah, I'm just confused why it isn't in any of the video descriptions like it usually is. I just looked at the Elder Scrolls and Avowed one-shots, which were done at a similar time to the Assassin's Creed one. The art for both of those was done by Julie Dillon, and the art style is also similar. It's very possible that due to those details it was done by them, but there is no confirmation.

That's still helpful. Gives me a lead to follow.