History of The Lament

Acquisition

The Lament is a Solar Exotic Sword (chainsaw-style) obtained only from the Lost Lament quest, started by Banshee-44 in the Tower once you have finished Destiny 2: Beyond Light. Full steps are on the Lost Lament page. At the time the sources were written it was not available from engram focusing or a vendor; check the Exotic Kiosk / Monument status in game if you lose it.

Perks

Per Shacknews and Hold to Reset: Banshee's Wail (hold guard to rev the blade for extra damage and shield piercing, building stacks for stronger heavy attacks) and Revved Consumption (damaging a combatant heals you). Light attacks before a heavy build stacks.

Catalyst

Not covered by the sources checked; unconfirmed.