Antharas Watchman Gilmore:
The Cave Keepers and Cave Maidens protect the Abyss Jewel. They have hidden the jewel with their sorcery, so if you kill them as they attack, the power of their sorcery will weaken and the jewel will appear.
Destroy the jewel, bring back its shards, and meet Antharas Watchman Theodric. He will give you a Portal Stone. Theodric guards the entrance to Antharas' nest in the deepest part of the dragon's valley.
If there are any colleagues with him, tell them all to come see me. They must also go through the process and receive a Portal Stone if they are to help you fight Antharas.