You can track down Legiana in Coral Highlands while you're completing the "Embodiment Of Elegance" quest, but finding him is not easy, since the highlands can be one of the tougher areas to navigate. Head north in Coral Highlands until you reach the large, wide open area in Zone 8. Keep heading north until you see the large, climbable wall, and after a little looking around, you should start to see footprints and other signs of the monster. If you don't (make sure you are really paying attention though, since some of the signs are rather unobtrusive), stay the course and keep moving forward, towards Zone 13. The monster should be in one of the two places.Odagaron Location
You can find the monster Odagaron in the Rotten Vale, while completing the "Into The Bowels Of The Vale" mission, in the lower level of Zone 14. When you arrive in the area, you'll see some clues that Odagaron is in the vicinity, and a cutscene will play. Once the cutscene is over, continue to track him, until you confront him. Then, it's just the simple task of killing him, and you've completed the mission.