"Oh," she says, distantly and with perfect confidence, "that's bad."

"...sudden sourceless truth?" Pull everyone back, get started on radiation shielding songs, send a team in for the Silmarils now, I don't care if it kills them...

Yep. She has vague, vague ideas of how it's bad, nothing specific or outright prophetic but -

- it's bad.

It takes about three hours, but it's obvious what is happening after two. The mushroom cloud resolves itself into a humanoid figure. It is glowing terrifyingly hot. It is drawing its form together in the semblance of an armored Elf. And it's angry.

You know what they need they need a Siobhan the problem is Siobhan didn't even know she was a witch until she'd already been a vampire for ages and there'd be no way to tell if she was or not and if she wasn't she would be much less useful as a strategist and also Elspeth doesn't have a copy -

Who have you got who was a witch before they turned?

In some cases it's genuinely hard to tell - she doesn't have Mama, Mama was immune to Aro - Dad wasn't before he turned - Alice was but she doesn't have any memories of her human life at all no telling what would happen to a fork of her and she has a mate - Afton was but he's not useful particularly and is out of the question on a personal level - Alec and Jane were but no Alec memories from after he decided to be okay with the usurpation - Chelsea was but fuck no - Pera was, maybe the mates won't be a dealbreaker when she doesn't have any memories from after she was mated anyway? - Vasanti might have been -

Then it's the Silmarils, I think. 

Chelsea sounds super useful but he is pretty sure Elspeth may actually murder him if he says that and at a minimum they'll both hate him for a while.

What do they even do?

They can be made to do most things that have to do with decay. Plausible ways of using them to stop that monstrosity are, well, stopping it from getting close since it's made of rapidly-decaying bits, and if our engineers are sophisticated enough and know what they're doing they should be able to stop all decay of all particles in its vicinity, which would just stick it there...

Well, stick it wherever it's gotten to by the time they figure that out.

Figuring it out will likely take months. Possibly years.

It's moving slowly but not that slowly.

Yep. I can evacuate people but it might move faster than evacuating people do. We could try using the Silmarils to protect various areas while we figure out how to use them to stop it, but that'll mean I need to pull everyone into one of three areas each with a radius of around seventy miles, I wouldn't expect them to be able to hold him off at a longer range without amplifying them somehow and the only people with a hope of figuring out how to do that are the people who will be trying to sort how to weaponize them - 

- is there any way at all you can bring back people in Mandos -

She doesn't have those people stored. She couldn't get them even if she made Aro and Addy artifacts and they worked perfectly and cooperatively. Aro had to touch living people.

My father always said the Silmarils had bits of his own soul stored in them. If he wasn't exaggerating, and you had an Aro and an Addy...

Seems like a huge stretch.

Probably.

Well, the retrieval team has been dispatched. It could take weeks to find the Silmarils in the rubble. 

Thank you. Let me know if you require anything else.

Nothing accessible.

Yup.

The cloud starts marching south. They evacuate to within the walls of the city, and ask Elspeth to send the walls of the city all the protective enchantments they know. 

She can do that.

He sends more people to find the Silmarils. He does not need to impress on them what a priority it is.

The thing, whatever it is, leaves the ground scorched and impossibly hot in its wake.

She has pretty good temperature tolerance but not that good.

You can outrun it. Unless it's not moving at its top speed.

Which it doesn't have any obvious reason to be doing.