It’s out of topic, but:
You could complete it with less than 3000 TP if you bring 10 Healing Potions, 5 Axe Attacks, 5 Bomb Attacks, and 5 Dragon Attacks.
Note that costume quests difficulty is similiar to emblem trials.
I was able to complete the last stage of nature trials with 4x 3☆ and 1x 2☆ heroes with those items.
I know that the trials have been buffed since then (extra boss HP) but as you can see I still have plenty Dragon Attacks left to deal with that extra HP buff.
Even after the buff, I still complete the trials with team less than 2800TP frequently.
Does everyone got Gunnar as their first costume???