I have a beginner account with minimal investment.
At the moment, 282 stages of the Fairy Corridor have been cleared.The main team for clearing stages:

1. Tank – Eurion. An accessible character who fits the element and performs
   his role without skill upgrades and with average gear (the necessary
   amount of accuracy is not collected). Equipment, talent upgrades, and stats are shown in the screenshot below. For bottom stats – Defense, focus on Defense.

 

2. Healer – Torrin. An accessible character who fits the element and performs
   his role even without skill upgrades. But I upgraded and didn't regret it, I use Torrin almost everywhere. Equipment, talent upgrades, and stats are shown in the screenshot below. For bottom stats – Enlightenment and Defense, focus on Enlightenment, Defense, and HP. The Ancestral Protection set is great for supporting weak 2nd line fighters, healing is sufficient.

 

2. Armor break – Lossenia. Before upgrading Lossenia's skills, Rava was in this position. Also, Zharlot will perform well in this spot. Equipment, talent upgrades, and stats are shown in the screenshot below. For bottom stats – Attack and Critical Hit Chance – everything for additional damage. Holy Hunter set – for
   additional enemy control.

4. Damage/Control – Gardrus. An excellent, epic character whose ultimate skill breaks enemy formation, stuns, and reduces cooldown speed. Equipment, talent upgrades, and stats are presented in the screenshot below. For bottom stats – Attack and Critical Hit Chance – everything for additional damage. Holy Hunter set – for additional enemy control.

Also, the epic character Theodore will perform well in this position. His ultimate skill stuns enemies and reduces their attack power. Equipment, talent upgrades, and stats are presented in the screenshot below. For bottom stats – Attack and Critical Hit Chance – everything for additional damage. Holy Hunter set – for additional enemy control.The only downside of Theodore in this team is breaking elemental links, as he does not belong to the Permafrost characters.

5. Damage/Control/Support – Tia. An excellent support character, I always take her when enemies focus very hard on 2nd line characters. With her ultimate skill, Tia applies invisibility to ranged fighters, saving them from focus and redirecting enemy attacks to the Tank. Equipment, talent upgrades, and stats are presented in the screenshot below. For bottom stats – Enlightenment and Attack. The Brotherhood Spirit set increases elemental damage for teammates, which is just what a support character needs.

At lower levels, when opponents are not so tanky, you can take a damage dealer or another control character instead of Tia. Also, her effectiveness decreases if the opponent's team has many 1st line fighters and your DDs on the 2nd line are not hit very hard. I also often used Voresh in this position. With artifacts for armor break, and also with the Holy Hunter set, he copes excellently with his task. Here are his talents:The team for clearing the boss will differ from the team for clearing regular stages. The main difference here is that the boss applies poisons, so it is necessary to take characters with abilities that grant Immunity to debuffs (Torrin, Tia, Catherine) or those capable of Dispelling debuffs (Torrin, Frubat, Oggok, Nathaniel, Fitz, Vicuc, Enna, Gumm, Eches). The second distinctive feature is the absence of a tank.
Therefore, my team looked like this:

1. Healer – Sifris;
2. Character removing poisons – Oggok;
3. Support character – Adolphus;

4 and 5 – Damage dealing characters – Felicity with an armor break artifact and Flora. These are very strong heroes, dealing good single-target damage.
The plus of this team is that all characters belong to the Wildfire element, which allows for maximum bonuses.