The Forgotten Tomb can be reached from the Sleeping Sanctuary and Graveyard, or by using the Teleport Rune from the Mist Harbor.

Route 1: Prisoner's Cell → Avenue of the Convicted → Deep in the Prison → Ossuary → Black Bridge (BOSS) -> Sleeping Asylum -> Forgotten Tomb

Route 2: Prisoner’s Cell→Poisonous Sewer→Old Sewer→Nausea Cellar→Sleeping Asylum->Forgotten Tomb

Death is not eternal sleep.

​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Explore a huge castle with ever-changing rooms in the repeated cycle of killing and rebirth, and unlock the secrets of this dark and isolated island...!

Of course, the premise is that you can defeat the many guards guarding it.

The above is the "Rebirth Cell" game tutorial compiled by Huajun editor for you. I hope it can help you!