Mutanus the Devourer

Awakening ritual
After Anacondra, Cobrahn, Pythas and Serpentis are defeated, regroup at the entrance and speak to the Disciple of Naralex. Restore health and mana before starting the escort. Stay with the Disciple through the ambushes and defend the ritual against the snakes and ectoplasms; Mutanus appears at the end. Keep the group at the ritual until the event finishes, then collect the Glowing Shard if it drops.

Mutanus the Devourer
Elite HumanoidMutanus combines Naralex's Nightmare and Terrify with a nearby Thundercrack stun, testing whether the group can restore control without leaving the ritual exposed.
Abilities

Naralex's Nightmare
Puts the enemy target to sleep for up to 15 seconds. Any hostile action will awaken the target. Only one target can be slept at a time.
Stop Naralex's Nightmare before it disables the healer. If it lands, remove the magical sleep when possible rather than waiting for damage to wake the target.

Terrify
Terrifies an enemy, causing it to flee in fear for 4 seconds. Only 1 target can be terrified at a time.
Use fear prevention or removal when available. Return to the cleared fight position after Terrify instead of drawing Mutanus toward the Disciple.

Thundercrack
Thundercrack inflicts nearby Nature damage and a stun without a cast to interrupt. Keep ranged players outside the close group and maintain their health before a stun prevents recovery.
Tank- Engage Mutanus away from the Disciple of Naralex. Recover the cleared fight position after Terrify so the boss does not remain beside the escort during the ritual.
Healer- Keep the group healthy enough to recover from Thundercrack's damage and stun. Agree who can remove Naralex's Nightmare if you are asleep, and clear it from other healers when you can act.
Damage- Ranged players should stay outside Thundercrack's close area. Preserve an interrupt for Naralex's Nightmare and help remove sleep or fear when your class can do so.