I did a search for trial of nature and was surprised not to find an existing thread, but if there is one and I missed it please merge.
I was able to get together an almost maxed 5 star team and fell back to one very good 3 star for her special. I was surprised that I still had to use mana positions at the end, but I did have some bad boards. RedHood was really nice for this challenge as you could go into the last stage with 3 meat shields, all that healing and chao couldn’t mana steal.
It was an all woman team: RedHood, Liana, Evelyn, Athena (actually she is only at 4-60) and Melia. I could have brought a few 4 stars instead of melia, but liked her special and wanted an all female crew just for kicks. Melia held up surprising well, she never died and only got to half health once.
With a slightly better board at the end, I think I could have done it with no use of battle items.