Campaignstorming time! - Fitting the NPC puzzle together.

[A G Thing]

Looking into the sort of herald you might use the best I have come up with so far is an Elemental Weird on pgs 90-93 of MM2.

They have divine magic and if suitably corrupted by say adding a dread elemental twist to them they could even affect or seem more in tune with the undead.

Fire/pyre, water/blood and earth/grave all could perhaps work separately for what you need but maybe you should consider combining the three into some sort of paramental being. Just mix and match what you need of their abilities and give it the old Ravenloft twist.

Graves surround a bubbling pool of blood and a womanly form with a burning heart forms from the red liquid which steams and scatters a thin layer of grave dust around her.

You may need to nerf her a bit but just a little and much of that can just be by limiting her to using only one elemental aspect per round and lowering her caster level or such. You can also just make her pool not as deadly as well and that would lower problems though it should still be damaging if she wanted it to be.

But I will keep looking but this is the best I have come up with so far!

[Gonzoron of the FoS]

hmm.... I'll have to look them up. Seems like there are "Snow" and "ice" weirds in Frostburn. Take a look:
http://www.wizards.com/dnd/images/fb_gallery/83551.jpg

creepy, no? Seem to fit with Evening Glory better than fire elementals...

[Zilfer]

Indeed.

[DilisnyaRevenge]

Here are a couple of quick/random ideas that you might find useful... Note - I tend to be a bit more "cinematic" with my campaign, so they might not work for you, but maybe they spark an idea.

How the Vampiress knows PCs are there: The Vampiress has been in P-a-L for a while hunting The Stalker. VR (also hunting Cynthia, known to him as "The Summoner" on behalf of Lord B) in an effort to recover the lost books. The vampire discovers VR while he is following up on some clues. Assuming (correctly) that he may be looking for same creature, she puts a tail on him in case he turns up any clues. As you said, when the PCs arrive, the Werebat transforms and starts wreaking havoc. VR hears of the carnage and arrives to help, discovering the PCs. The Vampiress, tailing VR, discovers the PCs presence as well.

How to include VR, but not have him steal the show: The botched summoning attempt has the demon on the loose and it is out for revenge against Cynthia. It has caught up with her and is chasing her through a crowed area. VR has already met the PCs and is working with them on The Stalker case, but is separate from the party at that moment following up on some old business. VR jumps to action because of the danger to innocents (he doesn't notice Cynthia directly in the chaos, only a woman being terrorized by a demon), actually saves her and drives back the demon, becoming seriously injured in the process. Cynthia takes VR prisoner, telling bystanders she is rushing him to the "family doctor." She really intends to give VR as a "rebirth" gift to the Metus, for what better blood to give him upon rebirth than the blood of his greatest enemy? The PCs arrive at the aftermath, gather a myriad of clues and ultimately have to rescue VR from the clutches of his nemesis.

Good luck!

[Gonzoron of the FoS]

How the Vampiress knows PCs are there: ...

This is good, except it means that VR has been on the Summoner case for some time and not made any progress. I would kind of like the PCs to accompany VR as he goes to Balfour and studies the scene of the crime for the 1st time. But maybe Van Richten has been in town for a while for other reasons... Ah! Then Balfour contacts him to track the thief, not to bring his own copies of the books. (Which is good, in a way, since it doesn't like Van Richten produce his copies and instantly know what's missing.) Now, I've indirectly established scale IMC, and it's a 2-day trip at standard speed from P-a-L to Mordentshire. If I wanted VR out of the adventure at this point, I could send him back to M'shire to get the books, while the PC's investigate. But he wouldn't be back in time for the eclipse, unless he did a hard ride down and back, and he's got no reason to believe he needs to be in such a rush at this point. I think I like him sticking around, though, so maybe he sends a courier instead.

How to include VR, but not have him steal the show:...

I like this! Especially the "rebirth present" idea. It's even easier to explain than him not noticing her because he's actually never met her! (Only heard about her from the PCs). On the flip side, she'd not know what he looks like, but perhaps she hears that the great Van Richten is in town somehow and orchestrates a trap. (By asking around, she might be pointed to him and introduce herself with a false name, or maybe there's a painting of him at the University or something). Of course, it will have to happen offscreen, or the PCs would never let her get away with it.