I guess I will be the first one to write a comment on this quest. You can get this quest at revered from the same quest hub you get "The Ashweb Matriarch". You go into the Hall of the Serpent and you see this big serpent floating up in the air. This mob has 4.7 million health, but it is not as hard as it seems.
There is a lower section and an upper section to this room. When you are in the lower section he does two things. He will spew lightning breath on a section of the room you are in. It will cover just about one third of the room. Simply move to a section it is not on. The other ability didn't seem to do much that I noticed. He throws a gust of wind that did 20-30k I think. As long as you are not low, it won't be an issue. As soon as you get a chance, move up the steps to the upper section. Melee will have to go up here right away as he will not get low enough to the ground in the lower area for you to melee him. He will just sit there spewing lightning, etc
It is much simpler to dps him up here. When you are up here, he will start shooting a bolt of lightning toward the spot on the floor where you are. You will recognize it by a big black circle under you. Staying in the pool will cause 20k dmg initially. I didn't wait around to see what it did after that, but the pools stay around for a little while. He does this a random number of times in a row, although it was usually four times from what I saw, never less and then you have a period of time where you can dps him before he does it again.
Eventually he will hit you with a gust of wind that knocks you back down to the front section of the room. Again try and get back to the top as quickly as possible as that is the best spot to dps him from. If you stay down at the bottom, there is very little room to dps him in as he will cover almost the whole ground with massive lightning pools.
Repeat this until he is dead. There is just one thing to be careful about. You can go out of line of sight past the pillar that he sits between BUT if you are in the wrong spot, the gust of wind can knock you against the pillar and then you just fall down to your death in some sort of chasm, lol.
All in all, a fun fight for a quest.