Altars of Sorrow

Altars of Sorrow is a guardian-initiated activity that can be triggered as a Public Event in the Sorrow's Harbor on the Moon similar to Escalation Protocol and Blind Well, where a team of Guardians must kill waves of Hive and Nightmares. There are five tiers of increasing difficulty and teams engage a final Nightmare boss at the end of their chosen tier, ending the event.

In reality, the Altars of Sorrows are rituals meant to sacrifice Nightmares for their Darkness essence for the Hive to utilize for resurrecting Zulmak, Instrument of Torment.