This is a guide for Mission 15: “The Trial of Lake Valor” in Pokémon Legends: Arceus (PLA).
How to Start Mission 15
You’ll receive this mission alongside Mission 14 and Mission 16 after speaking to Cogita at the Ancient Retreat during Mission 13, “Disaster Looming”. This mission also involves seeking a lake guardian–the one at Lake Valor.
1. Head to the Island at Lake Valor
Enter the Crimson Mirelands, via any of the base camps. Upon arrival, fast-travel to the Brava Arena and glide east-south-east towards Lake Valor. Or you may prefer to depart from the Diamond Settlement instead. Either way, land on the island in the middle of the lake and go up to where Adaman/Irida and Volo are.
2. Undertake Azelf’s Trial
Inside the newly revealed cavern, your first obstacle is dealing with the alpha Pokémon in the center.
If you intend to merely KO Overqwil (not advised), Ground-types are recommended. Although they’ll hate Ice Ball and Aqua Tail. Should your Ground-type get KO’d, Steel-types are good for back up.
Meanwhile, if you wish to capture Overqwil, Steel-types are preferable to resist Aqua Tail and take no damage from Poison Jab. If you did the Lake Verity trial beforehand, Hisuian Goodra is great for this; it can also use Shelter to stall.
Weakening Overqwil shouldn’t be too troublesome, but be wary of Double Edge, which inflicts recoil damage, potentially KOing Overqwil before you catch it. Steel-types or others that resist Double Edge will make Overqwil change its mind.
The second part of the trial is easy but tedious. You’ll receive some Marsh Balms and must throw them at Azelf, similar to the frenzied Noble fights. Well, you can try throwing them at Azelf, but it’ll dodge every single balm. Don’t give up and keep throwing balms at Azelf. Eventually it’ll acknowledge your efforts and you’ll receive Azelf’s Fang.
3. Report to Cogita at the Ancient Retreat
Having accomplished your goal at the lake, you’ll want to return to Cogita at the Ancient Retreat to update her on the situation. Volo will offer to escort you straight there. Or you could remain at the mirelands for a while, then leave via the entrance or by speaking to a Diamond/Peal Member at a base camp.