I know it was a 5th win prize on an event challenger but I have no idea how hard that opponent was and what the scroll might go for

It was from the masquerade 2013 plot after beating Blaire 5 times. I don't know much about battling but its stats were: Health: 12500 Strength: 4500 Defense: 3750 Speed: 2250

It looks like it went for ~250m in 2014 according to a post here

Hope this helps!

Ah I was looking for a previous pc post, I must have looked right over that one. That does help, thank you!