Piratecat
Sesquipedalian
A suggestion: if you really want to jump-start the campaign, forget that "under siege" stuff. Do something irrevocable that will shock the players... and nothing says "I'm not screwing around" like wiping out the most visible icon of the entire campaign world.As the party have been trapped in Farika for a month or more, I'm thinking that the City of Greyhawk should now be under siege by undead animals or something similar.
Do something awesome to it. Turn every buildings' walls into necrotic flesh that eats the living and vomits forth undead. Blast it with a plague that rips spells out of arcane casters and prevents them from ever handling magic again. Have the rock 30' beneath the city turn to soft mud for perhaps a minute... before turning back into rock, forever entombing most building and people.
Then think about the aftermath, and make sure the PCs know that the Mask was used in whatever happened.
Boy, will that get their attention.