ha, i had to dig this up from a previous post, here ya go
the cave of ordeals is in gerudo desert and it opens up once you warp the missing piece of the bridge of eldin back to is spot, the cave features 50 levels of increasingly challenging enemies, the first room of the the last room has only a few weak enemies, while the 49th features 3 darknuts(the big sword wielding, armor plated warriors).The 50th room ofthe cave of ordeals holds the great fairy, while in the cave you meet the fairy every ten levels and she asks you if you wanna leave, she also restores one spring(ordona, lanyaru, etc.) with fairies every ten levels, on the 50th level she gives you a bottle of great fairy tears(you can also get one bottle of these from jovani) great fairy tears restore all your health and turn you golden giving you a temporary attack strength boost, once you beat the cave, you can summon the great fairy at any spring in hyrule and the great fairy will refill your bottle(s) with fairy tears, the cave took me along time but it was definitely worth it. I hope this helps
oh, and a post like this deserves some rep right?