A dark staff made from an oak tree with grooves that twist and spiral along the shaft until it forms a hook at one end like a shepherd's crook. A black steel lantern hangs from the hook by a spiked chain and has a latch in the shape of a portcullis. While the lantern is empty, the staff serves no purpose other than acting as an arcane focus and a normal inspection reveals nothing unique about it other than the fact that it's magical.

Soul Binding

While empty, you can use a reaction to trap the soul of a creature killed in front of you that you can see. The latch opens by itself and there is no saving throw made as the creature's soul is instantly anchored to the inside of the lantern. Once bound, the lantern's outward appearance remains the same but the inside is transformed into a lavish castle interior that houses and provides amenities such as books, food, and bedding of a high caliber to the bound soul. The soul does not need these amenities to survive but is free to indulge in them over the duration of its imprisonment. Any attempt to manually open the latch in order to inspect the interior both instantly dispels the enchantment and frees the soul bound within. 

Spectral Lantern

Once bound, the soul emanates a spectral glow from within the lantern which illuminates a 30-foot radius with sickly green light. This feature costs no charges and can be controlled by the attuned at will.

Soul Charges

Any trapped soul always gives 10 charges regardless of the creature it belonged to. You can use an action to expend 1 or more of the staff's charges to cast one of the specified effects, using your spell save DC:

• (1 charge) Ghostly Wails - The soul's voice screams out in desperation and its cries sap the morale from your enemies casting Bane at 1st level without taking up concentration.
• (2 charges) Undead Interrogation - The staff creates a method of communication for the soul inside and allows the attuned to conversate with it under the same rules as Speak with Dead, with the exception that you gain the benefits of speaking directly to the dead creature's soul. Meaning that the spirit can learn new information, comprehend things that happened since it died, and speculate about future events.
• (5 charges) Spectral Warrior - The lantern's latch flies open and a plume of smoke bursts forth forming a specter of the bound creature within 10 feet of you. This creature uses the specter's stat block to determine it's abilities and actions regardless of what they were in life. It follows any verbal commands given by you and shares your initiative. The soul's true essence is still tethered to the lantern, and so, after a minute passes or their hp drops to 0 the specter's form dissipates back into smoke and is sucked inside again. If all charges have been expended, then the smoke merely evaporates and the soul's essence is untethered.
• (10 charges) Undying Loyalty - The staff pushes the soul's life force to its limits causing necrotic flames to begin leaking through the lantern's thick steel mesh that emanate an aura of entropy felt by anyone standing close enough, including the caster. All that energy is expended into casting Animate Dead at 3rd level instantaneously, with the added benefit that any undead created in this manner is permanently loyal to the caster until it's destroyed.

While bound, the creature's soul is tethered to whichever plane of existence the staff is on and can't move on or be revived until all of the soul's charges have been exhausted, the attuned frees it willingly, or the latch is simply forced open by another creature. 

Notes: spellcaster