The Graveyard Gate

From publisher blurb: 5th Edition Mini-Dungeon for five characters of level 6 A century ago, two dwarven brothers named Breodan and Lareck Deepwell gave their lives to save the surface world. As the rest of their clan held back an army of ghouls, Breodan and Lareck selflessly sacrificed their souls to seal the gate that would halt the undead horde’s advance. In doing so, the brothers forever trapped the ghouls (and their doomed clan) in the lightless tunnels of the Underworld. A solitary watchtower stands above what scholars now call the Graveyard Gate. Recently, a necromancer named Avinex discovered the site of the Deepwell Clan’s last stand. Avinex now works to undo the magic that sealed the Graveyard Gate and release the ghoulish horde. The heroes may arrive at the tower to thwart Avinex’s plans, or they might seek to open the Graveyard Gate for reasons of their own.