Ghostly Citadel

This massive tower of black stone rises from the centre of the Dead Plains of Ergoth like a single thin pole with a multi-spiked peak that can be seen for miles around. From a distance the tower seems hazy and indistinct like a mirage, however if the party come closer during the day they find that this is the natural state of the tower. It is ephemeral, fading in and out of existence but never becoming more than a ghostly structure. Attempts to touch
or pass through the ghostly tower make a creature feel like it is under great pressure. The footprint of the tower is roughly 120ft wide.

The tower becomes solid only at night, slowly forming and returning to the material plane as the sun goes down, becoming fully formed and non-ghostly as the sun disappears below the distant horizon. In this state the party find that the black stone is smooth, as though the tower were grown rather than assembled, and on the northern side a massive set of 20ft high doors of the same material stand silent and bare.

As the tower becomes solid, so too do ghostly figures begin to encircle it, grim figures that drift in the air, ever patrolling the grounds around the tower when it is fully formed.