I see... very good, then, in that case it makes sense. I'm particularly relieved that a pre-existing portal is indeed necessary to leave Urbaniel, since it would be rather superflous with guardians of the realm if anyone with a grain of power at their disposal could just draw up a portal of their own and/or recite an incantation to leave from anywhere in the realm. It also explains how the Carnival can travel around the realms so easily to make appearances for new audiences. The bit about powers seems a bit vague, still, but I suppose that's fine. I wonder what spontaneous reactions the use of powers could provoke, though?
And if I may ask another question inspired by your own reply just now: staying in a single realm changes you? How?

I am here, in case that wasn't already clear. And I'm, eh, sorry about... you know.