The Trial of Lake Valor

Description: In order to obtain the Red Chain, you must clear the trial set by the Pokémon that protects Lake Valor in the Crimson Mirelands.

When you go to Lake Valor, your Arc Phone will react and open up a hole in the cave. Inside you will find an Alpha Overqwil which will challenge you. Defeat it and Azelf will appear. it wants to play with you so creates some Marsh Balm and asks for you to try and hit it. It will keep asking if you want to give up but continue on to succeed in the mission and get Azelf's Fang