Zurrernorn is a secret society that deals with the undead.  An rouge from the guild mentioned them while bringing the part up to speed on the local underworld but didn't go into to much detail.  Partially because they are considered to be weaker than the enforcement branch of the Eight Fingers gang which the party had (justifiably) dismissed as weak, and partially because she didn't want to admit her ignorance about a group that is generally good at the "secret" part of being a secret society.

Soreiryu's never met or heard of Clementine, at least not under that name.  Speaking of names, scrying by name is pretty limited to begin with and assumes the name is unique.  YGGDRASIL enforced unique names for PCs and the most plot important NPCs, but doesn't seem to true of local first names.  The blood can be used to scry its source, which is Peter.  However, its possible to scry items you're familiar with and thinking about this may prompt the realization that the corpses are missing their guild badges.

He'll scry those, then, and then go looking for any hairbrushes or combs to try and find Nfirea directly.

[Locate item] plus a map borrowed from Lizzie place the badges in the graveyard.

[Clairvoyance] reveals a woman, presumably Clementine, wearing a bikini made out of adventure's guild badges.  On the bright side she has a young man that matches Nfirea's description with her, and all of the undead are low level.  On the bad news front they have a literal army of undead.  Also, present are a creepy old man and gaggle of hooded cultists for whatever thats worth.

Ugh. This is probably something Takeko will want to know about. Contacting her's at least easy enough...

Takeko's plan is loosely for her and Kuchinawa to go invisible, and try to draw the horde out of the graveyard (she suspects they're planning to attack the city, in which case they'll reveal themselves - as members of Takeko's team, trying to dissociate themselves from the undercover work here) while Soreiyu sneaks in to disrupt the horde at its source.

The most likely reason for kidnapping Nferia would probably involve his Talent, given he's not nobility nor a fighter, which means he might be being used to activate magic items to sustain the horde...

He first heads to Lizzie to tell her that his scrying revealed that Nfirea is in a graveyard, and that the woman who kidnapped him is raising more undead.

Lizzy will attempt to notify the relevant authorities.  Luckily her and Nferia are both local celebrities so she has some pull.

There is a place which occupies roughly a quarter of E-Rantel’s outer ring, which is also most of the western quadrant. It is E-Rantel’s communal cemetery. While other cities have their own graveyards, none of them are as big as this one.

This is in order to suppress the spawning of the undead.

Although many things are unclear about the spontaneous genesis of the undead, the basic idea is that vile creatures frequently spawn from the places where the living came to an end. Of these, people who died sudden, violent deaths and the dead who are not properly revered have the highest chance of coming back to unlife. Therefore, battlefields and ruins tended to be infested by the undead.

Since E-Rantel is very close to the Empire and consequently its battlefields, it requires a huge graveyard — a place where remains could receive the proper veneration.

In this aspect, the neighboring country — the Empire — also adheres to their common agreement to respect the dead. Though they slaughter each other, they both see the undead that attack the living as their common enemy.

In addition, there is another problem with the undead. If left unattended, the undead spawn more powerful undead. This is why the city guards and adventurers patrol the graveyards day and night to exterminate the weaker undead as soon as possible.

A wall surrounds the graveyard. This wall is the boundary between the living and dead. While it is only four meters tall and could not compare to the city walls, it is wide enough for people to walk on top of it. The large doors set into its side are sturdy and can not be easily breached.

All this is in order to ward against the undead that spawn in the graveyard.

There are staircases to the left and right of the doors, and watchtowers along the length of the wall. The guards take turns observing the graveyard below them as they yawn from the watchtowers, in shifts of five men at a time.

The graveyard is lined with sconces enchanted with [Continual Light] spells, so there is ample illumination despite it being nighttime. Still, there are many shadowy places, and visibility is even worse in those places blocked by tombstones.

The guards at the main gate to the cemetery have just came to a very important conclusion based on their own observations and reports from the surviving members of a patrol unit.

“The undead! The undead are everywhere!”

Takeko identifies the gate most likely to be swarmed, rings it with successive layers of magical traps as quickly as she can (while staying invisible), then positions herself and Kuchinawa between the gate and the horde.

And then, as the undead approach the first line of traps - 

She drops her invisibility, raises her hand, and clenches her fist in time for a very large explosion that ripples through the front lines of her enemies.

And then she brings her fist down, points, and speaks, and rays lance from her finger.

Kuchinawa isn't as specialized in fighting, being more of a healer-slash-support, but he's better against the undead than against the living, and has a few area of effect spells he can spam to thin out the horde.

Soreiyu casts no spells, and does his best to make no sound once invisible, maintaining his scry on the graveyard and waiting for an opening to retrieve Nferia.

The guards are panicked by the explosions, but also gather that the undead are being destroyed so they fall back.

Nferia continues to be surrounded, by cultists but the creepy guy moves foward to a position where he'd better be able to deal with a more conventional forward assault.

The undead keep coming and they don't stop coming.  Nothing strong enough to cause direct injury, but many of them are strong enough that suppressing them en mass requires relatively high tier spells like the 4th tier holy ray.  These spells are still far short of what they would use in YGGDRASIL PvP, where even 7th tier spell are highly situational.  However, PvP battles tend to be over quite quickly and yet still often hinge on MP management.  While it will take at least half an hour, probably longer if the locals start being remotely useful, holding back an unending horde will eventually use up all the guilds magic.  

It is not going to take Soreiyu half an hour to move into position. Maybe two minutes. He'll evaluate possibilities: grab Nferia and teleport away if he can, drop the creepy guy from behind and then start killing cultists as fast as he can without hitting Nferia.

Even players have trouble penetrating [Perfect Unknowable] so if Soreiyu spent one of his 9th Tier spell slots on [Perfect Unknowable] it would be trivial to fly in grab Nferia and teleport out.  Alternatively if he spent a 9th Tier slot on [Gate] he can just yank Nferia through.  Lesser stealth and teleportation spells could have issues with detection from anyone close to player level, of course by local standards they should be just about foolproof.  On the other hand this horde of undead qualifies as legendary by local standards.  Killing the cultists should be easy if thats what he focuses on, the only potential problem is if they target Nferia themselves.

He has both Gate and Perfect Unknowable, because his high-level-combat strategy is "don't" and someone on the team needed utility spells, since Takeko's too much of an aggressive dumbass to take them.

Nferia will disappear from the graveyard and reappear in front of Soreiyu.

There will be a brief rent in the fabric of reality, but none of the casters have particularly fast reflexes or anywhere enough talent to cast [delay teleportation] so it will be over and done with before they even notice.

Nfirea is extremely out of it.  Like its surprising he can stand.  He's also wearing all sorts of weird clothes. [Detect Magic] + common sense suggest the crown is the main issue.  [Appraisal Magic Item] suggests that the crown on his head should massively boost the power of any women already capable of casting mid tier divine spells and make it easier for her to blend her magic into that of others by enough for her to participate rituals despite taking enough of a mental hit to be effectively non-human.  It also suggests that removing the crown without destroying it first will permanently destroy the wearers mind, however it is worth noting that [Appraisal Magic Item] doesn't include full predictions for the item's interactions with effects not being appraised.

He doesn't have the spell, since he had limited seventh level slots, but he has a scroll for [Greater Break Item].

(If that fails, killing Nfirea, removing the crown while he's dead, then resurrecting him remains an option of last resort).

He is still out of it, but should mentally recover. It looks like the previous bleeding from his eyes may indicate some physical damage to them. Its hard to tell with the hair.

He knows some really basic healing spells, but first he's going to focus on getting the other items off. Can they be safely removed?

Surprisingly that is the only inherently magical item on him.  The rest of his outfit is either only important in the context of the ritual, or just flat out for the look of things. 

These people are idiots.

He'll coax Nfirea to remove the stuff that's required for the ritual, then, out of an abundance of caution, and then go to find the guy's grandmother.

Since this type of ritual isn't used in YGGDRASIL caution will result in a nearly naked Nfirea.

Lizzy is at the adventure's guild, where she has succeeded in getting the guild master to talk to her after hours and almost got forces mobilized.

He'll get Nfirea dressed, message Takeko about the ritual being ended, rouse a neighbor to stay with Nfirea, a different person to run a message to Lizzie, and then he'll scout the graveyard again, update Takeko again.

She wants to push forward with herself and Kuchinawa, but wants Soreiyu to play assassin against the cultists. Joy.

He'll go perfectly unknowable and return to the graveyard, then.