Ethereal Fury

The rage betwixt planes.

An Ethereal Fury is a vagrant Ethereal spirit that may imbue itself within any weapon that has been in the Ethereal Plane for longer than five minutes. They are especially drawn to weapons that have dealt fatal damage within the past hour.
Once imbued, the weapon cannot affect other creatures or objects on the Material Plane.

While attuned to an Ethereal Fury, your attacks deal an additional 1d6 Psychic Damage. The Ethereal Fury also grants one use of the Fly spell per Long Rest. These effects last until the weapon is destroyed.

After each long rest, players attuned to Ethereal Fury unwillingly enter a Trance and roll a d20. The result will submerge your psyche in one of the following Trance States.

• 1-5) FERVOR: Your thoughts are flooded with haunting, ineffable roars of bloodlust. Gain disadvantage on all saving throws until your next Trance.

• 6-10) FEAR: You’re late. Very late. You must hurry. Double your available movement in combat and reduce your Ability Scores by (-1) until your next Trance.

• 11-15) FAVOR: Your Trance is surprisingly refreshing. Gain 10 temporary Hit Points.

• 16-18) FOCUS: Everything is clear now. You understand what you must do. Gain advantage on Insight checks until your next Trance.

• 19-20) FURY: You find yourself obsessed with an old grudge. Suddenly, this weapon explodes with Ethereal energy (destroying the weapon and dealing 5d8 force damage to each creature within 30ft), then summons a Nightmare that will obey your commands and remain friendly to you and your party until its hit points fall to 0.