I'm pretty sure the maximum ranks the thunderdome could have is 10, for the same reason that a fireball at PL 10 is limited to 10 ranks.<br/><br/>Once again, i could be wrong, however if you put the thunderdome into your multipower then you'll be abel to maintain it while doing anything else in your mulitpower, but if it costs 10 power points to make a rank 10 thunderdome and 20 power points to have your personal force field at rank 10--both of which are proper to the power level of the adventure--then you could throw up the thunderdome to protect someone, then leave it up next round while doing stuff from your mulitpower.  :)<br/><br/>