Burden

 is a great sword in.

Acquisition
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 * Notnok's Lair can be entered via the Burrowed Hole where you enter the Restricted Section from the southwestern room in the Quarantined Section.

Upgrades

 * Note: Denial / Guilt are mutually exclusive.

Trivia

 * Because of the existence of a sketch image for Burden, it's likely that it was originally indented to be a soulbound weapon.
 * The icons for Burden were present in the game files with the release of, but the weapon wasn't actually in the game until.