Other than the main Campaign (link) and a variety of different 'generic' missions, X:Rebirth contains a number of unique or rare, side plots.
Base game:
- Treasure hunts (link)
- Craft: Rare Engine (loot drops; repeatable)
- Craft: Rare Weapon (loot drops; repeatable)
- Craft: Unique Shields (unique, fragile components)
- Craft: SETA (4.00 beta; loot drops)
- Craft Jumpdrive (4.00 beta; mission chain)
- Operation Forge Guard: A unique chain of generic missions for the Argon (link) rewarding a unique licence (warning about major bug here)
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