Abyss bosses can be located in the Abyss region found in Parliament Square.
To spawn an Abyss boss the player must first accept a quest from NPC Titus in Parliament Square, and then close 5 Hellrifts which correspond to their respective Boss. These rifts can be found in instances around Parliament Square which are: Lower Parliament, Upper Parliament, Brompton Cemetery, Westminster Catacombs, Middlesex Guildhall, East Treasury, West Treasury. After 5 rifts have been closed the quest will alert the player that a Boss has appeared in the Abyss.
"Find the Rifts. Seal the foul tears between world. When the masters come to inspect the damage, kill them without hesitation." ~Titus
Talox can be spawned by closing 5 Spectral Hellrifts.
Monster type: Spectral
His Lieutenants have the same invulnerable period that players have after they spawn, meaning they cannot be immediately damaged after they appear. The boss can launch multiple fireballs at players, and heal himself, which can be prevented by poisoning him.
Talox will spawn a pack of Lieutenants with different abilities in a specified order. The SFX of their damage type will penetrate the players shields resulting in a quick Stun, Phase, Shock or Ignite however, their attacks will continue to normally damage your shields first. The SFX attack strength is so high the effects will probably proc immediately after using status removers. There are 5 types of Lieutenants, and Talox will spawn packs in the following order:
Using an electric beam at range, and an electric nova at close range which heals them while casting.
Using Spectral Bolts and occasionally spawning a Tempest cloud which will do a deadly amount of damage should the player stand under it.
Shoots multiple physical projectiles at the player. Using a mini Smackdown on the player starting with a few seconds windup, they will first mark the player with a white beam which follows the marked target. After the mark appears under the player (similar to the mark of Hellfire attacks) the beam will no longer follow, and the player has a few seconds to get out of the way. The mini Smackdown attack will be deadly should the player stay in range. Physical Lieutenants will be instantly resurrected 2 times after being killed, but the resurrected version will have less amount of HP than the original.
Shoots a toxic projectile that penetrates any surface and will hit the player, leaving a toxic field around the impact point. These Lieutenants are more likely to flee from players than others, but continue to attack from very high distances.
Shoots multiple fireballs at players, and casts fire fields at melee range. These Lieutenants will attack more aggressively than others.
The boss will spawn each of the Lieutenants in a pack.
After the last wave the boss will continue to spawn these packs in the said order again, but the Lieutenants will have more damage and HP. The boss will become vulnerable after you defeat the second stage, and will be able to spawn 2 more of the Mixed Wave.
Squadro can be spawned by closing 5 Electrical Rifts
Monster type: Demon
Squadro uses EMP blasts and a unique version of spectral bolts, which shoots two heat seeking bolts. He will use a unique version of Firestorm when a player is at close range. He will spawn a pack of Winged Gremlins, gaining an impenetrable shield while doing so. The Gremlins will have increased amount of HP and damage compared to regular mobs. Ranged Winged Gremlins can spawn with an F-S Rail Pistol which can do significant amounts of damage. Luring Squadro away from his adds is the the best strategy for defeating him.
Dreadnaught can be spawned by closing 5 Physical Rifts
Monster type: Beast
Fightning Dreadnaught consists of 3 stages.
At this stage Dreadnaught will frequently shoot a unique version of rebounding bolts at all direction, and reflecting all kind of damage back to the attacker. Frequent use of Health Injectors, or skills with healing ability is necessary. Blademaster's Aura of Deflection can destroy the Rebounding Bolts,while Aura of Vengeance can return these projectiles to the attacker.(In this particular case the boss will reflect these projectiles back at the player.)
Dreadnaught gets smaller, no longer shoots Rebounding Bolts, and will only reflect projectile attacks. By gaining a special aura he gets faster and deals more damage with his melee attack.
Dreadnaught gets smaller again, loses all of his reflecting capability and will only attack with his default melee attack. Dreadnaught can burrow into the ground now, and heal himself while doing so. Healing can be prevented by poisoning Dreadnaught or standing at melee range while he is burrowing.
Fulcrum can be spawned by closing 5 Fire Rifts.
Monster type: Necro
Fulcrum cannot be damaged until 8 of his Master Totems are defeated. He will shoot a series of fireballs at players at mid range, using his stomp attack at melee range, which leaves a burning field for a few seconds. Occasionally he will attack with a regular melee attack. His melee attack is usually followed by spawning a Totem.
Fulcrum spawns the following Totems:
Enchants the Master Totem with Venom Armor, which will launch a devastating swarm in the players direction every time the Master Totem is hit. Hitting the Venom Totem itself will also do damage to the player, but will do significantly less damage than hitting the Master Totem. While active, the number one priority should be destroying Venom Totems especially if you are playing with a party. The distance of this Totem from the boss or other Totems doesn't matter, it's buff to other totems will be active until it is destroyed.
Quickly heals the boss to full health while active.
Casts a burning field around other Totems.
Master Totem Master Totems have higher HP amounts than other Totems, and will spawn a pack of Firesnaps every few seconds while a player is near. The Master Totems are the key to destroying Fulcrum. After 8 Master Totems are destroyed, the boss will become vulnerable. Do not attack the Master Totem if there is a glowing green Swarm aura around it, this indicates that a Venom Totem is still active somewhere. Note: The boss won't spawn the last Master Totem until one is still active somewhere on the map.