So… little help?

[lolthfollower]

I have a basic idea for a campaign, involving someone in a position of power getting polymorphed by a cursed item into a mouse, while everyone else ponders his mysterious disspearance, not knowing what happened, but I don't know where to go from there. I have a few details I know, involving someonein a position of power doing it, and when the plyers defeat him, he comes back and they find out it was a simulicrum they defeated, but that's all end-game stuff.

[Talar]

In mouse form he can speak, but only the PC's can understand him for whatever reason you want? The person responsible left a cryptic message/poem so people still know that the person is still alive/in danger/whatever. I think making this a mystery type campaign might be your best bet. You could also go with the classic an evil cult is behind it in order to attempt to grab power for themselves.

[Phelix-Mu]

Due to a magical oath, the BBEG can't actually harm the VIP. So he turns the VIP into a mouse. But now the mouse is looking to reveal the scheme, and the BBEG has to keep people from believing the mouse. So the BBEG tries to convince the party member that can hear the mouse (maybe the one with the most ranks in Listen) that hearing a mouse talk is a symptom of insanity. Maybe all of the animals start talking to the PC in question, whispering little lies and crazy stuff.

But, maybe the BBEG is actually not the one being evil. Maybe this is all part of a Fiend of Possession's (Fiend Folio) plan to overthrow the kingdom, and the BBEG is just under the sway of the fiend. To exorcize the fiend, the party must find the whatsit or cook up a special elixir or whatnot.

Have a subplot or two involving a looming war with the neighboring kingdom, angry fey in a nearby forest, or a strike by local lumberjacks that keep coming down with a mysterious illness.

Bam, campaign!

[Hexalan]

Maybe the Mouse-man is actually Evil, and has been stealing, exploiting, etc. lost treasures and the like for years. The other powerful character is very terribly vexed, and has managed to gather enough allies to stage a coup. His sense of honor prevents him from simply killing his liege, so he puts a powerful curse on an important item that had just been stolen and brought to the Mouse-man. He then plans to seize power through existing provisions for the disappearance of an official, and co-rule with his allies.

[Pluto!]

The curse is actually a Dispel, and the king was a mouse in disguise all along! The ostentatiously wicked advisor who gave the king the cursed item did so to cover his tracks and conceal his identity from the throne's hidden rodent usurpers!

The party members don their cloaks and daggers to intrigue their way to the bottom of the secret mouse coup - a recently-awakened ancient evil hivemind slowly who is steadily grasping possession of the kingdom's weakest minds of vermin and birds, and reaching further into the Derro and Kobolds. Soon, stronger willed humanoids will fall into its grasp!

[lolthfollower]

The curse is actually a Dispel, and the king was a mouse in disguise all along! The ostentatiously wicked advisor who gave the king the cursed item did so to cover his tracks and conceal his identity from the throne's hidden rodent usurpers!

The party members don their cloaks and daggers to intrigue their way to the bottom of the secret mouse coup - a recently-awakened ancient evil hivemind slowly who is steadily grasping possession of the kingdom's weakest minds of vermin and birds, and reaching further into the Derro and Kobolds. Soon, stronger willed humanoids will fall into its grasp!

That is… certainly the most creative idea I've seen.

[mr_odd]

The curse is actually a Dispel, and the king was a mouse in disguise all along! The ostentatiously wicked advisor who gave the king the cursed item did so to cover his tracks and conceal his identity from the throne's hidden rodent usurpers!

The party members don their cloaks and daggers to intrigue their way to the bottom of the secret mouse coup - a recently-awakened ancient evil hivemind slowly who is steadily grasping possession of the kingdom's weakest minds of vermin and birds, and reaching further into the Derro and Kobolds. Soon, stronger willed humanoids will fall into its grasp!

That is… certainly the most creative idea I've seen.

Dude, I love this idea. Suppose the king wasn't the only mouse in disguise. The party has no idea who is a mouse and who is a humanoid.

[Captnq]

A LITTLE HELP FOR THE ACTIVE DM:
When in doubt, Punt.