Oh right, I forgot: Sky Eye has incorrect description for weakness/immunity.
Found the last key, I really just got lost in the place and missed it.
Thanks for motivating me to check even further! I missed the chest blocked by a purple flame in the "room" that I noted in my "Heh, this flame's trying to hunt me but can't reach me." from my latest posted comment!
Ah, the Hollow General. This is gonna be tough! But I just kited him! Woo!
Have you figured out what Deciphering Scroll III reveals?