I can't help thinking that some kind of bastardisation of Die Hard with Winter Fae might be fun.
The local Winter Baron and Baroness are throwing the annual ball in celebration of the First Snowfall of the year, at an extravagant palace north of the city. It's a gala that lasts the entire weekend. One of the ballroom dance floors is converted into a skating rink, and the Baron/Baroness uses their magical power to coat the venue in what mundane guests would believe is artificial, realistic snow.
The players end up getting invited somehow. They are guided by a friendly Winter Court changeling who tells them what food is safe to eat and what food should be avoided. They are given luxurious accommodations and are safe from any Winter Court shenanigans thanks to the rules of hospitality.
A summer court changeling by the name of Sevarius Gruber, assisted by a dozen gruffs, including an older one named Karl, suddenly emerge to take everyone at the ballroom hostage. If the player's are attending, their gear might not be with them since it's a ball, not a combat zone.
A scuffle emerges, but somehow, Gruber and the gruffs are ignoring the effects of winter. He demands that the Baron and Baroness give him Mab's Fire, a powerful gem that is the anchor for winter's seasonal magic in the area. Winter is too powerful, and he has taken it upon himself to do what Titania refuses and restore the balance to natural levels. The Baron refuses, saying that he can't, for the gem is not actually his to give. Gruber produces a sinister wand that *could* be made of the same material that was used to make the Blackstaff and kills the Winter Baron. If the players look at it through the Never Never, it will be not quite as bad as looking at a skin walker, but close.
Other winter court fae move to intervene, sacrificing their lives in the process, as the Baroness retreats into the recesses of the palace, possibly assisted by some of the player characters. Gruber activates a powerful ritual, and the palace is surrounded by a fiery ward that burns with Summer's rage, preventing anyone from leaving.
The player's learn that Gruber's wand can only kill an immortal once per hour, but he threatens to start killing lesser fae that are dear to the Baroness unless she gives him the gem. In the meantime, his team begins casting rituals to break into the warded vault that is supposed to contain it.
All this activity attracts the White Council, who send in a team of Wardens, led by Warden Johnson and Special Warden Johnson. They cordon off the area and look for ways to dispel the fiery ward, with anti-summer magic ritual.
The anti-summer ritual will also take out the last of the wards in the vault, which is what was used to protect the Gem from other amibitious Winter Fae.
The players eventually learn that Gruber isn't a Summer Changeling. He's a powerful, lawbreaking sorcerer that is consorting with an Outsider. His gruffs are chaotic, shapeshifting abominations and the plans for the gem have nothing to do with restoring the balance. You might say he's nothing but a common thief, but the truth is that he's an exceptional thief... The wardens know how much lawbreaking he's done, and are prepared to shoot first and not ask questions to ensure that no Outsider influence leaves the premises. Mab knows the severity of the Outsider threat as well, and is okay with this scorched earth approach since her Winter agents powers have been neutralized.
If some of the players are on the outside, they have to manage the threat on the outside.
