After completing the mission Metis Legacies in Outward, another quest will begin - the Ash Giants. To complete it, first go to Chersonese.
There, go to Conflux Mountain. Around midway up the mountain, you will find the entrance to the Blue Chamber's Conflux Path. On the site, you will meet many different opponents. Make sure to, first of all, take good care of your health. If you deplete most your health points, retreat, heal your hero and then fight again.
Over the precipice, in exchange for your health points and stamina, you can unlock Mana. This will allow you to create runes and spells. If you get Mana, you'll complete the mission.
In this location, you can also find 3 other magicians, they can help you improve your skills.