Reminder: I tried to use as less Action Cards as possible so you can follow the steps easily. But if you have good Action Cards, you can use them if you want, as long as it doesn't disturb the instructions I gave below.
There are a lot of enemies here, and they have lots of HP too. It's recommended if you have a deck with at least 1 character that can heal or create a shield. But in my case, I use Overload Deck so the enemies will swap a bunch of times and disturb their elemental reaction rotation. Below is the Sharing Code for the deck I use if you want to use the same strats.
In my video playthrough, the most important Action Card would be Katheryne because you need the Fast Action in the later Rounds. Other than that, you can change any Action Cards you want.
Sharing Code: AdAg4xoOATAw8U4PBBDg8k8PBEDw9rQPC2BA97UPC3FQDbcQC9GADsMQDOEwD80QDPAA
What you need to know about this enemy is that she has a passive skill that allows her to gain Energy. More specifically:
After this character takes DMG: If this character has no greater than 7 HP, the gain 1 Energy. (Once per Match)
Even worse, other Eremites also have the same passive skill. That's why it's easy for them to use Elemental Burst early on. Another reason why I use Overload Deck; is to force them to switch to the next character and disrupt their opportunity to use Elemental Burst.
First of all, start with Fischl as the starting character. Make sure you obtain at least 2/3 Electro Dice and 2/3 Pyro Dice (even better if you got Katheryne Action Card right from the bat). If not, restart the challenge until you get the dice I mentioned. Follow the steps below after that:
Fischl's Skill > Switch to Bennett (DO NOT use any cards that make this a Fast Action) > Bennett's Skill > Use Katheryne's Action Card > End the Round before the opponent
Notes: The reason I told you not to make the switching character a Fast Action is because if you do that, you will use Bennett's Skill on the Scorching Loremaster and we DON'T want that because it will make her gain another Energy.
Switch to Xiangling > Xiangling's Normal Attack > Xiangling's Skill > End the Round before the opponent
Notes: By the end of this round, I hope you already have the Katheryne Action Card activated because you need that Fast Action in the next round.
Xiangling's Burst > Switch to Fischl (hopefully you got it Fast Action) > Fischl's Skill > End the Round before the opponent
Round 4 & 5:
RECOMMENDED Best steps: Fischl's Skill > Fischl's Burst > After Fischl died, switch to Bennett > Bennett's Skill > End the Round > Bennett's Skill
My Youtube video steps: Fischl's Skill > Switch to Bennett > Bennett's Skill > End the Round > Do anything you can to inflict reactions and kill the last enemy
Important: In my Youtube video above, I switch to Bennett instead of using Fischl's Skill, which is a mistake. But I still won with that mistake (using Food) so both steps are okay, although I recommend using Fischl's Burst more as it is much faster.