|Estinien and you will face off against Faunehm. For the first part of the fight Estinien will use Skydragon Dive shortly after you engage and tank, allowing you to hit your positionals. Make use of your buffs during this time to take advantage of the extra damage. Abyssic Buster is a large conal attack, and Heavensfall will chase you with AoE circles. Occasionally after Heavensfall she'll follow up with Comet, a proximity AoE.
The biggest problem move is Chaotic Verse. This will do moderate damage and inflict Enervation, lowering damage dealt and increasing damage received. When she does this to Estinien he will use Elusive Jump and get Orn Khai to help him recover. This means you'll be tanking the boss for the next portion. She'll mostly just spam Dark Star, an arena-wide AoE, but you'll still need to dodge the occasional Heavensfall and Abyssic Buster. Keep it up until she uses Chaotic Verse on you, then use Elusive Jump and head over to Orn Khai while Estinien goes back to tanking.
These mechanics will repeat until she hits 0% and the fight finishes.