I'm having trouble understanding just what the consequences of his return are. And just what is going on in the Shadow Play encounter anyway?

About the scenario: What are the PCs supposed to learn here? What has happened to Sinophia? They have fallen to cultists and chaos because the Imperium have abandonend them as they focus their efforts against Haarlock? What is the sybol of 3 scratchmarks? Is this just supposed to show that letting Haarlock return is bad?

More generally, I guess he will take revenge against all who opposed him, and then take the fight to the Slaught? What happens to the surviving worlds of the Sector? They serve a new master now? Denounce the corpse-emperor and embrace Haarlocks reign?

I think the whole Blind Tesseract Scene is to impose on the players a feeling of "Damned if you do , Damned if you don't" situation. The three scratches are purely cosmetic to differentiate members of the cult from others.

The scenario i think goes as follows:

-Erasmus returns and start to methodicaly dismantle the Imperium's control of the sector.

-The Slaugh sensing all is lost attack, only to be completely trounced.

-The Imperium reels, abandoning whloe swathes of the sector in an attempt to consolidate it's base in order to strike back at Erasmus.

The real question is what sort of power exactly has Erasmus at his disposal. Is he something like a Chaos Lord, with an army of Cultists and bound Daemons? Or something else altotogether.