Hybris

"Horrors are pieces, slivers of greater crimes. I am pride with reason. I enslave the whims and wyrds, the dreams from the other side of the Veil. Face me! Face everything!"

Hybris is an ancient personification of pride, naturally making him a Pride Demon.

He can be found by completing The Awiergan Scrolls: First Aspect, The Awiergan Scrolls: Second Aspect and The Awiergan Scrolls: Third Aspect, and then starting The Awiergan Scrolls: Pride Unbound by entering the Hidden Dungeon on the northeastern side of Darktown, south of Anders' clinic.

Strategy
The Boss Fight:

The key to fighting Hybris is understanding the mechanics. First and foremost, his health bar is enormous, so this won't be like the pride demon fights from Dragon Age: Origins. It will take a lot longer, and involve a lot more effort. This fight is seperated into two phases. The first phase is the demon spawn phase, and the second phase is the tank and spank phase.

Phase 1:

Hybris begins the fight in a very nonchalant fashion. He'll hit your tank for a modest amount of health and seem like nothing more than an overgrown mob. This quickly changes, however, as numerous shades and rage demons will begin spawning. Immediately take all three of your other party members' attention away from Hybris and burn down the demons as quickly as possible. The longer they stay out, the more of a chance you'll have to fight them with the next wave of demons that spawns. If not taken down quickly, you'll be overwhelmed before you know it. With that said, the demon phase begins with about 2 shades spawning simultaneously. After about the third wave of shades, a rage demon begins to spawn as well. I found that taking down the shades, whose punches can interrupt spell casting and melee attacks, helped make the fight with the rage demon that much easier. The adds will seemingly last forever, but fret not, they do finally stop. A sign that you're about to be done with the spawning demons is when two rage demons spawn almost back to back with the two shades.

While this phase is going on, Hybris will charge himself for about 30-45 seconds with a green flame that will make his attacks much more powerful. A good way around this is to either kite him around during this phase or to keep your tank healed with potions and healing spells. It seems that once it happens, it's done for the rest of the fight.

Phase 2:

This phase of the fight occurs once all the demon adds are dead. Hybris will now be nothing more than a mob with a health bar too big for his own good. His damage is negligible at best, and can be easily taken care of with some potions or a few heals here and there. His attacks remain the same throughout the remainder of the fight.

Attacks:

His primary spell consists of summoning a blue circle on the ground which, after being cast, lies dormant for a few seconds. When he smashes his fists on the ground, the circle will warp and begin to pulsate, trapping any of your party members who walk within it, dealing periodic damage and making all movement impossible for around ten seconds. The damage done is negligible, even to a mage, but can be devastating if you're surrounded by mobs during the demon phase. As soon as you you see it, pause the game and move all party members to safety outside the circle.

His other spell consists of charging his fists up with a green flame that causes his basic punches to deal additional damage. There's no way to avoid it, but it can be almost entirely ignored if your tank has enough armor, defense, HP, or all three.

His final attack is a charge, similar to the one used by the Arishok. He reels back and a wave of energy surrounds his head, giving you about a second or two to react and move your party members out of the way. He'll usually use this when someone is trapped inside of the blue circle trap, but he does do it outside of that routine as well, usually when his aggro switches to a ranged target that he needs to quickly reach. The damage done by this is, once again, very easy to overcome, as it's more of a way to kill your DPS that gets trapped in the circle trap than it is to kill your tank.

Lastly, at the beginning of the fight he'll pulsate with green energy "veins" all around his body. This phase deals considerable damage to the tank, and is the only portion of the fight where any kiting or healing may be needed in addition to the potions. That said, he only seems to do it once, and afterwards will only ever use the green flame punches for the rest of the fight.

Strategy:

A good strategy is to have your tank (in this case Aveline) hold Hybris' attention AT ALL TIMES. During the add phase, never have your tank go fight off the demon spawns, as Hybris will run amock and kill of your DPS in a few hits if they're not bracing for impact. During this first phase, simply take your other 3 DPS (preferrably one melee, like Fenris, and 2 mages) and have them burn down the adds. This fight can also be done with three mages, so if you choose not to take a melee, make sure you have ways of stopping the rage demons, else they'll hit away at your low defense mages and kill them off. Ice damage works well in conjunction with Horror and Hex of Torment to burn down the rage demons ASAP. Using Anders as a healer, his haste allows your DPS to quickly burn down the shades in a mere matter of seconds. This entire phase should consist of nothing but you avoiding the blue circles, and burning down the adds as quickly as possible.

Once the adds stop spawning for good, you can focus on Hybris. Since he is vulnerable to crowd control spells like Horror and Petrify, use these to your advantage should your tank ever go low on health. Otherwise, simply use Hex of Torment and some magic spells, or whack away with some melee DPS and he'll eventually go down.

Notes:

An optimal party setup for this fight would be a tank (Hawke or Aveline), 2 ranged DPS (preferrable two elemental mages, one of whom is specced into entropy, the other being specced into healing), and a melee DPS (preferrably a 2H warrior, as they'll soak up more damage). The other optimal setup is a tank and 3 mages, the third mage being some sort of entropy/elemental or entropy/primal mix for all the crowd control and hexes. In essence, your party will be:

Tank: Hawke or Aveline. DPS : Fenris (Melee DPS), Anders (Healer/DPS), Hawke (Melee/Magic) or Merrill (DPS/Crowd Control/Hexes) Healer: Hawke or Anders (Healing DPS)

or

Tank: Hawke or Aveline DPS : Merrill (DPS/Crowd Control/Hexes), Hawke (Melee/Magic), and Anders (Healing/DPS) Healer: Anders (Healing/DPS)

Resistance: some fire runes will be useful to stave off most of the rage demon damage.

Potions: Plenty of healing potions in case of any unforseen actions taken by the boss during the fight where the party's healer is unable to help. In addition, plenty of lyrium potions and stamina draughts. As the fight can reach up to 10+ minutes depending on the party makeup and DPS, it's wise to be prepared for the long haul.

Revival Potions: Bringing along Mythal's Favor is also recommended. As it is quite possible to be overwhelmed by the staggering amount of demons that spawn, having some form of Plan B to revive the main tank or healer is strongly recommended.

Trivia

 * The achievement "Demon Slayer" requires the player to find and kill Hybris.
 * Hubris (pronounced /ˈhjuːbrɪs/), also Hybris (from the Greek; the letter upsilon is sometimes transliterated as "y" and sometimes as "u" in English words derived from Greek), means extreme haughtiness or arrogance. Hubris often indicates being out of touch with reality and overestimating one's own competence or capabilities, especially for people in positions of power.
 * The Hidden Lair is also the entrance to the Amell's Cellar