Sister of Silence Eris:
Anybody who goes in the Casket Room is considered an intruder. Only 3 of her disciples, Eris, Kaerun, and Anays, the inventers of the seal devices, are permitted.
I cannot directly help you because I can't leave here. Thus, there is no way in except to destroy the seals. But the seals are protected by the 4 Guardians of Relics, they will stand in your way.
Ask about how to defeat Guardians.