The grey-white, down-hanging tendrils of the Banshee Willow give it it's name. The tree is difficult to find, even in the boggy marshes of it's natural environment. Travelers beware, for these trees seem to attract ghosts and other unsavory undead.
The Banshee Willow seems out of place in contrast to the dark hues of swamp, almost otherworldly. Spirits of the dead seem to linger near, drawn to the magic of these ashen willows.
The truth is, the Banshee Wiilows exist as anchors, bridging the physical and shadow realm. Many Geistspeakers craft their staves out of Banshee Willow to amplify their powers.
Additional Ideas (3)
An ancient Banshee Willow acts as the source of a powerful curse that afflicts a nearby village. The dead do not remain dead, but instead become zombies that can speak but no longer control their decaying bodies. Cursed to witness the deaths of their family, friends, and fellows, the heroes are contacted/asked to save them all and let their souls move on in peace.
The village of Ashen's Fall has always seemed to attract an eclectic bunch of spirits and undead. The village was named after an epic battle that took place on the south end of town. Thousands perished as the old kingdom of Ashen made its last stand and lost hundreds of years ago. There are priests permanently assigned to the village because it is such a nexus of paranormal activity and undead creatures that move through their small streets and bustling market.
Over the years a Banshee Willow has grown deep in the woods north of the town. Over time its power has expanded and drawn restless spirits and even animated skeletons from the battle of Ashen's Fall. They are raised from the battlefield in the south and make their way north...directly through Ashen's Fall.