Blaudewedd didn’t create the ice in the Bitter Reaches. Ferenblaud did.

As written, Ferenblaud is bound to get out of his ice prison

The summer elves cursed Ferenblaud and the land with permanent magical ice, locked in by Seals. Blaudewedd’s magic has hidden the location of the Seals from e.g. Wurda (p. 49), but the passage of time means that the summer elves don’t know where they are either. The Ice Giants, whose job it was to guard the Seals, have dwindled in number and been abandoned by their creators, who haven’t once come back to see how they’re going, or to remind them that there’s some magic “spark of life” in a cave right next to where they live that can restore their fallen numbers to life.

The Orcs, Redrunners and Ice Giants should be natural allies, but distrust each other for various reasons.

Ferenblaud is encased in ice on his throne. His trusted Prince Namtarel likewise sleeps in his “tomb”, saved from Blaudewedd years ago (he’s getting better now).

Each of the Seals is guarded by monsters who once served Ferenblaud. There’s one Seal per element (elemental magic being the sorcery that Ferenblaud’s sorcerers were good at, and that the druid Blaudewedd decreed to be evil and wrong - p. 21).

Breaking a Seal gives you a minor magical talent and makes the weather nicer, so the campaign assumes the PCs will think “Ooh, an adventure: open the door, go down the corridor, kill the monster, get the treasure”; but if they don’t, other meddling adventurers, rampaging armies who don’t know any better, or flat-out servants of the Winter King will break them instead.

What would you have expected the summer elves to have done?

So it’s 3,000 years ago and the winter and summer elves have just fought a bitter civil war, but the land is otherwise fine, and all the other kins are looking forward to the war being over and being able to get back to their normal life. Even better, the summer elves have promised them that they won’t have to be slaves any more. They’ll head back to the Stillmist just across the mountain pass to the South and get out of your way, but if you need their help you know where to find them.

As for Ferenblaud and his closest associates, well, they’ll have to pay, so the summer elves are going to take their rubies with them, so they can be locked away in the Stillmist / face justice / be turned into better people / whatever happens to bad elves.

If any ice monsters can’t be dealt with, you would expect the elves to find other kin who could learn ice magic and make sure any remnants of Ferenblaud’s troops, currently hiding away, are dealt with when they resurface. The orcs could be good candidates, given how they resent Ferenblaud for having enslaved them.

The absolute last thing you’d expect the summer elves to do would be to dabble in Ferenblaud’s ice magic, which they reject and abhor, to cast a giant spell of ice on the entire realm, including Ferenblaud and his captains, making everybody else’s life a misery; to anchor it with elemental magic seals guarded by Ferenblaud’s favourite monsters; and then to wander off.

The ice curse is Ferenblaud’s backup plan if he lost the war

It makes a lot more sense to understand the ice curse as one last bit of “if I can’t have the realm then nobody can!” vindictiveness from a powerful ice sorcerer tyrant who can conceive only of two things: (1) him being in charge and (2) him not being in charge at the moment.

After all, if you’re an immortal elf, the one thing you don’t fear is the passing of time. If you have an enemy who’s currently more powerful than you, and you have no way of beating them at the moment, the best strategy is to outlive them. Your enemy also being an immortal elf makes this more of a challenge, granted, but if the alternative is to surrender to them - meaning death or, even worse, a change to your lifestyle - there’s no real choice, is there?

Sure, the local people might hate you at the moment, and your victors might have determined to make sure you never come out of your self-imposed ice prison, but memories fade, institutions weaken, and it’s not going to be too long before people start wondering if they can do anything about this horrible ice spell. Meanwhile, you’re not going anywhere - “Ferenblaud’s prison is also his greatest defence (see page 71). As long as two of the Seals are intact, the Winter King is encased by magical ice, immobilizing him but also protecting him from all harm” (p. 289) - and e.g. Namtarel is getting better (p. 198).

The best clue that this is self-imposed? The fact that Ferenblaud and other winter elves have been freezer-burned. “Three thousand years of frozen hibernation have left their mark, however. His skin is thin and withered, his eyes sunken and bloodshot, which makes the king’s face look like a grinning skull with a forehead furrowed by endless ruminations.” (pp. 71-72). “The winter elves are tall and proud but have a harrowed demeanor. Their skin is pale and withered, a side effect of being frozen for so long.” (p. 89).

Nonsense. The one thing we know about freezing is that it prevents decay - see, for instance, the contents of your freezer, Ötzi the iceman, or any science fiction generation ship involving suspended animation. Besides, elves can heal damage by “sleeping”, and can basically look like whatever they want.

No, Ferenblaud and his winter elves look like this because they have embraced the look of being ice elves.

What does this change to the campaign?

Probably not much. Ferenblaud is still locked away, and is still about to escape. The present day Redrunners still have the problem that they want to make sure that at least one of the seals is protected, so Ferenblaud stays locked away at least partially, but (1) don’t know where the seals are, and (2) have a real hard time saying to basically everyone “I know you want this terrible ice to be gone, but it’s going to be really bad if it goes”.

Their best strategy is still to (1) make friends with the orcs, ice giants, and basically anyone, while (2) finding one of the seals and defending it relentlessly / walling it up. The campaign is adamant that this can’t possibly ever happen, and that’s one of the reasons why I’m never going to run it, but it’s still what any faction should do who doesn’t want Ferenblaud to return.

As soon as one seal is broken, they should camp out in the palace of the Winter King and systematically kill any winter elf that turns up. Once the fourth seal is broken, they can now kill Ferenblaud, who doesn’t have his dragon or his support troops. They should even get support from any of the armies in the field, on the basis that fighting a war against one less army is always a good idea.

(As an aside: a campaign that is certain that it’s gearing up to a final epic battle between three or maybe four armies, should maybe spend more than a paragraph - p. 295 - describing said battle.)

Because that’s the problem with Ferenblaud’s plan: while he’s pretty confident that he’ll eventually be able to escape the prison that he built for himself, he’s still in prison.