Seshem.eff Er Aat is an Isu vault located in the Black Desert in Egypt. It is connected to the tomb of the nomarch Tefibi III, who had his final resting place built on top of the complex's remains.
Around 48 BCE, the vault was visited by the Medjay Bayek of Siwa, who activated the vault's pedestal and witnessed a recording made by the Nomarch messenger. Dated ninety-three days after the Great Catastrophe, the message displayed was intended for Layla Hassan, who was reliving Bayek's genetic memories in 2017.
- Seshem.eff Er Aat is a romanised version of the Egyptian "(sShm.f) (ir) (aAt)", roughly meaning, "Lead Him To Truth".