When you enter the frozen cave, there are 4 paths leading north. The rightmost path will take you to one boss fight. The two middle paths will both take you to another boss fight. There is also a boss fight at the top center, but it looks like you need to find a way to enter the map that's directly above and then dip down into this first map.
This first map has an exit at the northeast corner. That leads to a second map that will eventually branch off to the north and continuing east. If you take the lower east path, you'll come to a dead end where there's another boss battle. The guide says you need to use the item 'Unholy Scriptures' which is found in the big underground warehouse in the monastery. If you take the northern path which then heads east, you should trigger a fight just after you pass a cul-de-sac to the south. Continuing east leads you to an exit.
The guide then says that if you return to the same cave after delivering the stolen idol, you'll need to kill the enemies again and you will get a Butterfly Shield. It also looks like this is when you can enter the map that dips down into the first map, but I can't be certain of that. It does look like there are several coffins that line this particular map before it dips.
That's all I can decipher from the guide. The guide is pretty vague. If it helps you, great, if not, I tried.
