Need help with a campaign idea, set in the tippyverse.

[purpenflurb]

I was recently shown the guide to the tippyverse (found here http://www.giantitp.com/forums/showthread.php?t=222007) and am rather intrigued with the idea. Particularly I was looking at the megacities, and whether it would be possible to subvert the system. What I came up with is, what if there was a small group of casters intent on evading the authorities of the cities?

What I have come up with is having some sort of mobile city, on a giant animal of some sort. A small population, probably 10-20 individuals, is for some reason running from the authorities. Further, I was thinking that they might try to help fight the influence of the cities in the wild areas or other planes, without being noticed. Similar to the star trek prime directive.

What I need help with, is how might a small group of people avoid an empire with powerful casters? What I want to go with is a giant animal capable of holding the basic structures on its back, I am ok making something up for this but if it can be done by RAW even better. This creature, and the citizens would then need some sort of protection. My thoughts on this were resetting traps to cover the citizens and the creature with mind blank and greater invisibility, and perhaps some sort of extremely high CL anticipate teleportation as well. These are just the basics though, I am not yet sure how they would escape if need be, or how they would prevent a lone scout from communicating back and teleporting an army in.

This is probably going to end up being a high level undertaking, but I would like it to occur at as low of a level and with as little expenditure as possible, there is very little glory in an epic level wizard managing to evade them. So, basically, what sorts of protections might a giant animal carrying a small village on its back need, and how might such a creature be created in the first place? Any help will be much appreciated.

[TypoNinja]

Stronghold Builders Guidebook actually has rules for making structures mobile, its expensive as all hell but doable.

This would probably be better for a solution standpoint, because then you could just dome your city, then permanently Sequester it via the wondrous architecture rules (same book). Rules for enchanting protective walls even mean that people inside the city can still see everything, while its all perfectly invisible and undivinable from the outside.

You can again, make it so that being inside its dome also confers whatever protective buffs you choose to keep everything hidden, mindblank, Set up a Forbiddance, that kind of thing.

Cost will be sky high on anything truly city sized, but it sounds like you are talking about something more like a small fort than a true city if it can be on the back of something (Turtles all the way down!), then again if this is your muguffin for a campaign, to hell with cost and just hand wave its existence, maybe it was built and improved over time. A very patient group of casters with Craft Wondrous Item and a steady supply of Ambrosia could get it done for pretty low cost if you don't mind it being constructed of shaped walls of stone.