Xorn Tunnels

From publisher blurb: Xorn Tunnels is a Fifth Edition plug-in adventure for four characters with an average party level (APL) of 8, 11, 14, or 17. This addon offers details for each level and makes adjustments accordingly. Flying high above the town of Darkwell is the castle of Tovin the Disfigured, kept aloft on caverns of enchanted bloodstone. Lately, a host of xorn have taken root in the caverns, drawn to the stone’s magic. The characters must enter the bloodstone tunnels and remove the xorn threat before they consume it all and cause the island to fall onto Darkwell.