Shroud

While the shroud appears as a dense fog, in reality it's made of condensed essence of the primordial element of death itself (Arcana Check 12). It's what contains Druskenvald and keeps it in its state of limbo.

It would be known that souls that are on route to Druskenvald must first pass through the Shroud with the assistance of Strangers. Without them, the Shroud would tear the soul to shreds and devour their anima.