The plane of Shadow is home to a mix of the living and undead. These days, living souls who dwell in the Plane of Shadow are usually in thrall to an undead lord, who protects them in exchange for some service.
Dusktown is the preserve of Lord Ixlac, a polymorphed brass-ish dragon who employs the townsfolk to raise the cattle he eats.
Ixlac is an independent; he takes the long view and tries to stay out of the politics of shorter lived folk. Sometimes he meddles to maintain his own comforts. He also likes to collect interesting trinkets, such as Wulmthar's helm.
Ixlac is a 14th level Wizard, so he can help the party. The Banishment spell would work, with the minor problem that they would likely reappear in an area of the Prime Material corresponding to their current location. This is south of the border barrier and definitely in the zombie plague zone. Ixlac's plan is to transport them to the border and try to send them across in their own country.
There's a minor complication in the form of a rumour of a feud between the Lords of Seattle/Tacoma (LOST) and the Spokane Word Ancient Poet's Moot (SWAP Moot).
The SWAP Moot is a bunch of high level bards, mostly dub poets, but also some druids.
The border wall created to hold back the zombie plague on the prime material manifests on the plane of shadow as a weird hedge of coconut trees. Their trunks are joined side by side at the base, but about 6m up the trunks diverge crazily in all directions. The treetops are filled with monkeys, who hurl explosive coconuts at anyone who approaches the barrier, whether by land or by air.
SWAP Moot members include:
Hope Harmony - land druid
George Byron - bard
Ada King-Gnoll -bard
Maire Shelly - moon druid
Don Juan Tenorio - bard
Ixlac sent the party to Wulmthar's Keep, where they are to retrieve Wulmthar's crown. Ixlac tells them he needs the crown's magical energy to accomplish their return to the prime material plane.
On their way back from the keep, the party encounters a wagon heading south. It is driven by three figures. These are Oni (Filipevna, Triquet and Zaretsky), sent by Dmitry Larin to smuggle a load of mage weed to a mage tower at Chuska Peak.
The Lords of Seattle rule the northwest. Greatest among them were the mighty Amazon Hippolyta, Bill Gatekeeper (head of Marduksoft, a noted magical publishing house), Howard the Duck (head of Starducks) and Billy Boeing (the famous flying carpet and pogo stick manufacturer).
Recently the Amazon has come under the sway of Dark Prince Joffrey Beelzeboss, a vampire who has been engaged by Malacath to help bring the prime material plane into the plane of Shadow.
Haseya , the wizard of Chuska Peak, believes the distinction between divine and arcane magic is artificial. Her lifelong project was the development of her Grand Arcana Underlies Divinity Elemental Theory of Everything (GAUDETE). When she died and went to hell, she continued to argue for her theory and look for funding to continue her work. Malacath was sufficiently impressed that he set her up with a research lab in the Shadowlands. Her assignment is to apply her theoretical work and merge the Shadowlands with the prime material plane. Malacath thinks that mageweed emerged as a side effect of some of her experiments, so he is shipping her a sample to analyze.