The Lost City of Amdaphor and the Sineaters

[Zohar_Lahar]

At most we can assume the Sin Eaters as we understand them are identical across the shards. It's very possible that there have been Sin Eaters that came into existence on the Source at some point and that is what the constructs of Amdaphor were based on. Whether there were actual Sin Eaters involved like the Voidsent in the War of the Magi is not really clear.

Part of the problem is Shadowbringers still hasn't explained where Eden came from, and why it beget the Flood of Light and sin eaters.