[ericthered]

I think a strict reading of RAW gives you +10 for changing worlds + 10/quantum. The +10 is 'per dimensional boundary'.

If I were setting up IW to work with RPM and trying to preserve the feel, you would either be limited to a single quantum jump, forbidden from crossing boundaries at all, have a steeper progression on changing worlds (10, 40, 90, 160,..; 10,20,40,80,...), or you add an additional greater effect each time you cross a quantum boundary. Quantum level is a big deal is IW, and default RPM makes changing worlds very easy.

Yrth has none of the standard spells for world travelling work. They're actually known, and research on working versions is a thing. Conveyors and those with the jumper advantage enjoy a -20 to all attempts to leave (though getting their is easy). The agent who got back did so is implied to have done so with the raft of worlds, a world-jumping artifact strong enough to overcome yrth's resistance. For RPM, I'd rule that there is a big greater create cross roads effect that spans the entire continent (the banestorm), and the rules on stacking spells means you have to overcome that spell before you can go anywhere. Demon summoning works because its a lesser effect.