Kostchtchie in Storm Kings Thunder?

[WalterO’dim]

I've had a soft spot for Kostchtchie since I first saw the demon lord on the cover of Dragon Magazine #119. At some point in the new few months, I will start running SKT. I am new to DMing so I stick pretty close to script but I can't help but wondering: Wouldn't the Demon Lord of Frost Giants try to take advantage of the break in the ordning? If so, how? Perhaps he or his minions would be seeking the Ring of Winter in order to conquer the realms?

I found a products on the DMs guild that lists Kostchtchie as a CR21, so I'm guessing that he wouldn't make an appearance until very late in SKT or, perhaps, even after the climax.

So, any thoughts or advice on incorporating Kostchtchie in Storm Kings Thunder? Always looking for existing material...

[Composer99]

You could easily have Kostchtchie replace the dragon who is the adventure's primary antagonist. If he's a higher CR than an ancient blue, you might need some more storm giant NPCs in the final chapter so that he doesn't crush the PCs like bugs.

[Unoriginal]

I don't think Kostchchie was referenced or mentioned in any of the 5e books, not even when mentioning the Frost Giants who quit the Ordning (when Baphomet or the god of trolls are described as attracting those who do, IRRC).

So if you want to include him, you pretty much have a blank check you can fill however you like.

CR 21 seems pretty appropriate for a not-major Demon Lord.

As for the schemes he could do, well, keep in mind that while an artifact like the Ring of Winter would be a huge boon, being able to show up in person would be even better. I'd say that having the Giants open portals to the Abyss in order for his demonic minions to invade Faerun en masse, followed by Big K himself once it gets big enough.

[WalterO’dim]

Sooooo...What kind of minions would the big old Frost Lord bring with him from the abyss?

Anyone have a good point in the adventure to introduce this baddie?

[Quoxis]

Sooooo...What kind of minions would the big old Frost Lord bring with him from the abyss?

Anyone have a good point in the adventure to introduce this baddie?

IIRC Volo‘s guide to monsters has stats and fluff for frost giants that enter demonic pacts for greater power, occasionally grow new heads and limbs, and if they get found out they’re shunned by society, losing their place in the ordning etc.
You could have an entire tribe/cult of frost giants like that, mixed with warlock spells and invocations (imagine frost giants with eldritch smite and armor of agathys!) as devotees of Kostchtchie regularly attack both the PCs and other giants until the players decide to end that by crushing the cult, potentially getting some recognition among the more peaceful giants, opening up new ways of diplomacy - or they can side with the demonic frost giants and bring down the ordning altogether, if that’s not too derailing for your campaign.

[WalterO’dim]

Cult of Kostchtchie served by 2 headed frost giants...sounds fabulous! I’ll have to check out Volos.