Is any reason given for the Blackstaff magic item trapping the souls of its owners on death?

Question

I have the Blackstaff. How can I be resurrected? asks how you might go about being resurrected if you're the Blackstaff (the title of the wielder of the Blackstaff magic item; yes it's confusing, I'll italicize it when I refer to the item).

Background

I think the answer to that question (especially how it interacts with clone, where there is no clear reason to assume the staff or clone has precedence on the soul) may ultimately depend on the lore, and specifically, why the Blackstaff traps the souls of its wielders on death.

Is there any reason given in the lore for this behavior?

I feel like if Khelben Arunsun had strong feelings on "you only get one life to live" it might make sense for it to override clone (it may have been intentionally designed to prevent someone ruling Waterdeep forever by foreclosing on options like clone), but if it's for some other reason ("the gods won't get my soul!" or "when your time as the Blackstaff is done, you serve/advise future Blackstaffs [Blackstaves?] by contributing to the collective of souls housed in the staff for the benefit of Waterdeep") it might make sense to treat clone (which instantly transfers your soul to a living body on the death of your current, so the soul would never be unhoused, even for an instant) as being meaningfully distinct from other forms of raising from the dead (which are explicitly prevented).

Question: Is there any lore behind Khelben Arunsun or his Blackstaff that explains why it traps the souls of any wielder who dies, not just Khelben himself (who is trapped, but remains the dominant personality in the staff, with meaningful control over it, to the point of being able to recreate the staff, even if splintered, from a single piece, at will) especially any information that would indicate whether clone violated the spirit of the staff's design?

The staff is a 5E item, but lore from any edition would be useful.

Answer 1

This Property is new to 5e

The Blackstaff as a magic item in the game did not used to have this Spirit Trap property. In 3rd edition, found in Forgotten Realms Campaign Setting, the Blackstaff is just a staff of power with a permanent spell (also called blackstaff) applied to it:

The black staff (a staff of power with a permanent blackstaff spell upon it that allows it to dispel magic as an 8th-level caster by touch, channel various mind-affecting spells, or cause a touched spellcaster to lose a prepared spell or expend an unused spell slot.

The Dispel Magic, Drain Magic, and Master of Enchantment propeties fit this old description, but Animate Walking Statues and Spirit Trap are new.

The Spirits Used to be Linked to the Tower

In the old lore of the Blackstaffs, found in the novel Blackstaff Tower, the memories of the Blackstaffs are stored in kiira N'Vaelahr which then manifest as spirits in the tower.

With this original lore, neither souls nor spirits are bound to the Blackstaff or Blackstaff Tower. Instead, a version of the Blackstaffs memories are retained through the magic of the kiira.

The Clone Spell in the Old Lore

Using this old lore, the clone spell wouldn't violate the intent of the staff's design at all since the apparitions in the tower are simply manifestations of the Blackstaffs memories.

Khelben built this into his Blackstaff so that the past Blackstaffs could serve as advisors to any future high wizards in Waterdeep. As such, clone does not violate the spirit of the weapon since it was never intended to prevent reincarnation to begin with.

The Clone Spell Today

Interestingly, the Spirit Trap property doesn't actually trap souls, it traps spirits. Compare the language of Spirit Trap...

When the Blackstaff dies, the spirit of that individual becomes trapped in the staff along with the spirits of the previous Blackstaffs. (A Blackstalf whose spirit is trapped in the staff can't be raised from the dead.)

...to the language of a similar magic item like the lich's phylactery:

It does this using the imprisonment spell. Instead of choosing one of the normal options of the spell, the lich uses the spell to magically trap the target's body and soul inside its phylactery.

The fact that the Blackstaff is only trapping the spirit into the staff and not the soul indicates that a spell like clone may work (but ask your DM and read on for some reasoning). In fact, reincarnation magic would work if the property didn't specifically prevent it.

It stands to reason that the term "spirit" in this context is comparable to the memories that were stored in the kiira in the past.

Speak With Dead

There is some similar language in the speak with dead spell that is of particular note:

This spell doesn’t return the creature’s soul to its body, only its animating spirit.

I would posit that this animating spirit is the same entity that the Blackstaff traps as it serves a similar function: extracting information from memories of a dead creature. This fits with Khelben's original intention with this property in the lore.

The soul would still move on to an afterlife, but this could justifiably prevent reincarnation (as even if the soul is free, without an animating spirit, how can you reincarnate).

This could be a justification for a DM to disallow clone from functioning as well, since it would allow your soul to pass to the clone, but your spirit would still be trapped.