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Perhaps the Fane have in service some cleric who can stand in as an intermediary. While the soul might refuse to be brought back by a cleric of Lloth, perhaps a cleric of the Svirfnebli, the Kuo-Toa, or some other sect known to the drow would be willing to do it (for suitable payment or coercian), and would pass the post-mortem sniff test of the soul being pinging for resurrection.

Perhaps the Fane have in service some cleric who can stand in as an intermediary. While the soul might refuse to be brought back by a cleric of Lloth, perhaps a cleric of the Svirfnebli, the Kuo-Toa, or some other sect known to the drow would be willing to do it (for suitable payment or coercion), and would pass the post-mortem sniff test of the soul being pinging for resurrection.

Raise the minion as a wight

What's that, the minion's spirit isn't willing to be raised? Wow . . . that is some loyalty. Well, use create undead to raise them as a wight.

Of course, the oaths they swear will serve our purposes just fine. Between that and the control that create undead gives, you ought to be able to peel them like an onion.

The reluctant soul

What's that, the minion's soul isn't willing to be raised? Wow . . . that is some loyalty.

Perhaps trickery will need to be called for. The DMG says about Bringing Back the Dead:

A soul knows the name, alignment, and patron deity (if any) of the character attempting to revive it and might refuse to return on that basis.

Perhaps the Fane have in service some cleric who can stand in as an intermediary. While the soul might refuse to be brought back by a cleric of Lloth, perhaps a cleric of the Svirfnebli, the Kuo-Toa, or some other sect known to the drow would be willing to do it (for suitable payment or coercian), and would pass the post-mortem sniff test of the soul being pinging for resurrection.

Okay, it's a long shot, but the dead minion's soul only knows the cleric's name, alignment, and deity, so it's not completely out of the question that they might take a chance to return to life.

Raise the minion as a wight

Or, use create undead to raise them as a wight.

Don't be too worried about the wight's "autonomy". Sure, the wight's description says "autonomy", but it also implies some sort of allegiance to "the dark entity [who] transformed them into undead" (the evil cleric raises their hand), and create undead says things like:

each corpse becomes a ghoul under your control

you can mentally command any creature you animated with this spell

you decide what action the creature will take

you can issue a general command

[t]he creature is under your control

Does the cleric have perfect control over the "autonomous" wight? No. But they have a lot of control. The wight is intelligent. It has sworn oaths to the evil cleric ("dark entity"). Create undead is exerting control over it.

All of that, and I think you ought to be able to peel them like an onion. But if you don't think so, that's what's important. And, fair enough, there's plenty of discrepancy between the text of create undead and the description of the wight, leaving a ton of DM adjudication just to make the spell work (like that's never happened before). It's pretty clear the writer(s) of the spell and the monster didn't carefully rectify the two descriptions against each other.

After all of that, even if the wight is uncooperative, detect thoughts can probe pretty deep, given a captive target and time.

Raise the minion

If I'm the evil cleric, I'm just going to raise the minion and then use mundane tactics. I mean, just how loyal is the minion? Once raised, if the minion can't be flat out bought, then surely they'll eventually succumb to some sort of influencing magic.

Planar ally comes to mind.

. . . while a fiend might demand a living sacrifice . . . .

"Hey, minion, welcome back to the land of the living. Come over to the dark side and wealth and power will be yours¹. If that doesn't appeal, well, say hello to my pit friend here. They'd like to make your acquaintance."

yochlol have detect thoughts

What, don't want to let your clerics use planar ally? That's okay. The yocholol have detect thoughts in their stat block.

Raise the minion as a wight

What's that, the minion's spirit isn't willing to be raised? Wow . . . that is some loyalty. Well, use create undead to raise them as a wight.

Wights possess the memories and drives of their formerly living selves. They will heed the call of whatever dark entity transformed them into undead, swearing oaths to appease their new lord while retaining their autonomy.

Of course, the oaths they swear will serve our purposes just fine. Between that and the control that create undead gives, you ought to be able to peel them like an onion.

Kill the zombie anyway

I mean, speak with dead is cheap. Maybe there will be some useful information.

And commune the heck outta those PCs

Every cleric 9th or above can cast commune once a day.

You contact your deity or a divine proxy and ask up to three questions that can be answered with a yes or no. You must ask your questions before the spell ends. You receive a correct answer for each question.

Surely that will help fill in any gaps left by the minion and zombie.

Don't feel restricted by the restrictions the PCs face

I know, I know. It sometimes feels like cheating to let NPCs use resources not available to the PCs. But it's not. The DM has to represent the whole world. There is plenty out there beyond the reach of the PCs, at the very least, they don't have time, they're busy adventuring. And your evil clerics have had centuries to perfect their art.

^{1 - in suitably small quantities, restrictions apply}

Raise the minion

If I'm the evil cleric, I'm just going to raise the minion and then use mundane tactics. I mean, just how loyal is the minion? Once raised, if the minion can't be flat out bought, then surely they'll eventually succumb to some sort of influencing magic.

Planar ally comes to mind.

. . . while a fiend might demand a living sacrifice . . . .

"Hey, minion, welcome back to the land of the living. Come over to the dark side and wealth and power will be yours¹. If that doesn't appeal, well, say hello to my pit friend here. They'd like to make your acquaintance."

yochlol have detect thoughts

What, don't want to let your clerics use planar ally? That's okay. The yocholol have detect thoughts in their stat block. Detect thoughts won't work on a zombie, but it will work just fine on the raised minion.

Raise the minion as a wight

What's that, the minion's spirit isn't willing to be raised? Wow . . . that is some loyalty. Well, use create undead to raise them as a wight.

Wights possess the memories and drives of their formerly living selves. They will heed the call of whatever dark entity transformed them into undead, swearing oaths to appease their new lord while retaining their autonomy.

Of course, the oaths they swear will serve our purposes just fine. Between that and the control that create undead gives, you ought to be able to peel them like an onion.

Kill the zombie anyway

I mean, speak with dead is cheap. Maybe there will be some useful information.

And commune the heck outta those PCs

Every cleric 9th or above can cast commune once a day.

You contact your deity or a divine proxy and ask up to three questions that can be answered with a yes or no. You must ask your questions before the spell ends. You receive a correct answer for each question.

Surely that will help fill in any gaps left by the minion and zombie.

Don't feel restricted by the restrictions the PCs face

I know, I know. It sometimes feels like cheating to let NPCs use resources not available to the PCs. But it's not. The DM has to represent the whole world. There is plenty out there beyond the reach of the PCs, at the very least, they don't have time, they're busy adventuring. And your evil clerics have had centuries to perfect their art.

^{1 - in suitably small quantities, restrictions apply}