Still putting together details for my Gencon event, and I would like to crowdsource some ideas for evothaum attacks made by genre savvy, nothing to lose Outsider cultists. They have a form of sponsored magic that allows for evothaum when breaking the 7th law, as well as for transformations and biothaum that corrupts or distorts reality. It's a one shot end of the world sort of game, so I'm not worried about horrific long term consequences for the PCs. They need to be afraid and in over their head. Any thoughts on what type of effects to throw around?

Is she established in Dresdenverse canon? And if not, is she just a powerful witch or fae?

She is a retired agent, off the force for over 20 years. She can have full on thaumaturgy. I'm seeing her in more of a enabling and party support role. Here are her aspects:
High Concept: Ex KGB Kitchen Witch
Trouble: Let Babushka fix it
Other aspects:
License to kill
This is how we do things in Mother Russia
A place for everything and everything in its place
Babushka is always prepared
My gentleman friends

Depends on the group. How combat capable are they, and do they know about the RCV catch (soft bellies and holy stuff)?

Your enemy trips. Into a pit full of spikes. That are soaked in gasoline. In the middle of a nuclear test site.

Bird-mancy veil.

A bird of paradise appears in all of its glory and takes a huge dump right in your opponents face, whilst you and your companions slip away in the confusion.

Geomantic transformation scene aspect

You bind the shade of a dead monster truck driver to your own, giving you his skill behind the wheel.

Photomancy skill replacement: Athletics.

You conjure a blast of light, blinding your opponents, who then blindly fire their pistols while your normally flabby wizard butt gets the heck out of dodge.

Pyromancy skill replacement: Rapport

Zone wide Flesh to Stone spell. Does regular damage, but taken out turns those hit into statues. Consequences also reflect transformative nature of spell.

Divination evothaum attack.

The caster divines then speaks the dread Seven Words that strikes the target at the core of their being, throwing their entire worldview and self concept into a spiral of doubt and despair.

Water Social Block

This is all good stuff-I especially like the bathtub. Thematically it doesn't fit, but I'm going to use it anyway. Part of what I'm trying to accomplish is giving the players more gruesome details to investigate. They have already rescued a group of church group kids that were going to be turned by the neo-reds, and now they plan to hunt down the source of the scourge. They had a blast killing red court vampires last session-as one player put it, it's hard to feel bad about doing anything to a red. Next come the repercussions to their little vampire slaughter fest. Discovering the extent that the big bad went to gain power will serve to show them how deep in the stuff they have gotten themselves into. Lets see how they feel about fighting assault rifle wielding saliva addicted middle class soccer mom goons.