No Man’s Sky
No Man’s Sky Forsaken: mementos and trader rewards
Haunting mementos come from infested outposts, deep-space hulks, derelict freighters and planetary digsites. Take them to Forsaken traders at space outposts for corvette modules; preserved grubs are also used for the Larva Cannon.
Choose a salvage location
The official update names those locations rather than a single best farm. Prolonged exposure while harvesting attracts hostile boundary horrors. Plan to leave danger when necessary; no exact safe timer or guaranteed drop rate is supplied by the official notes.
Sources: [1]
Trade the appropriate offering
Forsaken traders can be summoned at space outposts. Their rewards include cockpits, habitation modules and biomechanical hull structures. The Larva Cannon Multi-Tool specifically uses preserved grubs; the official page does not give a quantity, so do not assume every memento is interchangeable for that weapon.
Sources: [1]
Separate unlocks and courier contracts
Dedicated collectors can earn the Mind Harvester title and Larva Tank helmet; the official update does not state the exact collection threshold. Courier missions are a separate activity at deep-space outposts and require a corvette plus a Gravitino Coil. Cosmos deep-space materials can also be pinned in the Catalogue for location guidance.
Sources: [1]