FFXV Deadeye BehemothGo to the Nebulawood Parking Spot. From there, head to the forest and into the opening between rocks. Once you are there, a couple of Voretooth will attack you. When you pass them, crawl through the small passage and a cut scene will show the Behemoth. You will find out that his weak spots are on his right side, since he is missing an eye and a horn there. Jump over the fence to the foggy area and follow Deadeye to his lair.
Make sure you don’t let him see you or lose him, because you will have to start over again. If you are too close to him, fall back or hide behind the rocks. At one point, Deadeye will jump over the rocks. Head between the stones and you will find him in the lair.
Make sure you absorb the fire energy you find along the way and use it to make some spells, as you will need them for the fight. Once you are in the arena, you will see the oil barrels. The easiest way to defeat him is by using the Circle button on PS4 (B on XBox One), so you aim the magic and detonate the oil drums with Fire when the Behemoth is near them. If you are taking too much damage, avoid his attacks by holding Square (on Xbox One hold X). Remember that you can always escape to the nearest wall with Point warp, and choose a better place to attack him from. After you successfully hit him a couple of times with exploding barrels, he will be defeated.
Head back to the Wiz Chocobo station to complete the quest and the hunt.