Impact Oneshot 3

Spoilers ahead! Proceed at your own risk.

Impact oneshot the third (Beware all who enter, there be spoilers)

State of play:

The plan is to run a big fight, basically. Maybe have the PCs short rest beforehand.

Still need:

A reason for Rick to not be actively fighting the PCs (possibly a deus ex wizard from Perrin and Alice)
Some sauce for the fight, especially for the melee characters. Perhaps this is based off the weather - after all, a torrential thunderstorm is occuring in Geronimo as this is happening.
- Sauce idea one: some mechanic to make the big boss guy vulnerable and break his grapples. There's some thingimajig which attracts lightning, and they need to throw it at the chain devil in order to hit it with lightinging. One removes its resistance, and two makes it vulnerable, resetting at the start of its turn.
- Sauce idea two: the chain devil will swing you all over the place if you don't escape or break the grapple, and the two dogs its got as backup will do a high-damage grab on you if they catch you grappled.

The enemies are

a chain devil with the following changes:
- as much HP as i need
- multiattack is now one chain and one infernal chain
- regular chain attack has a follow-up - it can swing grappled creatures around a silly amount (2d10 on physical impact)
- infernal chain is flavoured as a 'plunge arm into ground' kind of attack and also grapples, but can't move you around
two devil dogs (custom enemy)
- they are leashed to the chain devil, and share its resistance to physical damage, retaining it even when the devil looses it.
- HP: 40, SPD 40, AC 17
- Slash: +4, 1d8+3
- Bite: +7, 2d8+5 (grappled enemies only)

Now what attracts lightning? Copper? other conductive materials?

In the carnage, a blacksmith shop has gotten smashed and there are a bunch of swords in the ground, sparking with conductivity
Each turn three are struck lightning, and then three 'light up' to indicate that they will be struck next turn.