Asterius the Taurus King

Asterius the Taurus King (アステリオス・ザ・トーラスキング) was the actual Floor Boss of the 2nd Floor of Aincrad in the official service of Sword Art Online. Asterius is supported by Baran the General Taurus and Nato the Colonel Taurus. The boss had six HP bars.

Appearance
Asterius's is a humanoid-form monster with its legs being as thick as tree trunks. Asterius's waist was covered with sturdy, dark chainmail, though the upper half of its body was bare. The taurus's head was that of a bull, but with six horns instead of two, that had a twisted beard hanging down to its stomach, and a round, silvery platinum crown atop the centre of its head. Asterius's body was black, as if painted with ink. The boss was armed with a massive hammer twice the size of Baran's.

Attack Patterns
When Asterius's eyes glow, the boss leans backward, sucking in air and its massive chest bulging like a barrel with little sparks crackling out of his nostrils, and the taurus then unleashes a long-range, lightning breath attack, which is capable of traveling the full length of its range in the instant it is unleashed and has a very high chance of stunning or paralysing its victims.

Like Baran, Asterius has a special debuff skill, called «Numbing Detonation» (ナミング・デトネーション), which has twice the effective range of Nato's «Numbing Impact». Players caught in the golden sparks released by the skill are rendered stunned for three seconds. If the same player is hit twice with the skill in succession, the stun effect is changed to a more dangerous paralysis effect. When Asterius is about to use this skill, it stomps three times in succession before raising its hammer.

Like Baran and Nato, Asterius enters a berserk state when it is close to death. This state is signaled by the boss's black skin burning through like coal.

Weak Points
Asterius's weakness is the crown atop its head that can only be reached with thrown weapons. Attacks against its crowns cause the boss to stagger.

Preparations
The raid party could not prepare for the battle, as they had no knowledge that a secret boss was added to the official service of the game. However, before the battle took place, Argo undertook a series of quests beginning in the jungle outside the Labyrinth that eventually earned her information on Asterius the Taurus King, including the boss's attack patterns and the best way to counter them. She was only finished turning in the quests after the raid party was already in the Labyrinth, thus she could not message them about the information she obtained and had to deliver it personally.

Summary

 * After Baran's last HP bar reached the yellow zone, Asterius spawned in the middle of the boss room and proceeded to advance towards the main part of the raid party.
 * Just as Baran is defeated, Asterius unleashes its breath attack, paralysing numerous players, including Kirito, Asuna, Lind and Kibaou.
 * Asterius attempts to strike Lind and Kibaou with its hammer, but his attack is interrupted by Nezha hitting its weak point with a chakram.
 * Argo informs the raid party about Asterius's attack patterns and how to counter them.
 * Nezha single-handedly keeps the boss occupied for over two minutes to give the other members of the raid enough time to recover from paralysis and refill their HP.
 * Lind orders groups A and D to attack the boss, relieving Nezha of having to keep the boss occupied by himself.
 * After some time, Asterius's HP bar is depleted to the red zone and it enters its berserk state.
 * The boss uses Numbing Detonation, forcing everyone except for Orlando's group, as well as Kirito and Asuna, to retreat.
 * Kirito and Asuna strike the boss's crown. Kirito deals the Last Attack.

Trivia

 * Asterius, alternatively spelled as Asterion, denotes two sacred kings of Crete, the first of which was the step-father of Minos, while the second is believed to be the Minotaur itself.