I joined a fight in Unicorn way, the second battle sigil from Olivia Dawnwillow (if that helps), the second that this battle sigil was activated, the whole region turned black, couldn't see the fight sigil. It happened both when I was in a fight, and view someone else fight. I don't know how to add a picture, but I got one of the bug.
While fighting decaying bogwalkers in the boiling fields, I noticed that the circle that showed how much health I had was off center, and so were the circles at the bogwalkers' feet. I tried fighting them again, and it was the same again.
Another thing I noticed is that if you receive things and hover over the circles in the corner of your screen that show what you got, if it is a treasure card an image of that treasure card will pop up, but if it is a reagent or a pet snack, only the name of it will pop up, instead of the item card.
I also noticed that it is possible to level up inside of the Deckathalon tower, because you get a small amount of experience for defeating monsters. If you level up inside it your health and mana are refilled.
[Edited title - please be specific in the title or we have no idea what bug you are talking about. Thanks!]