ULXs and blazars are two highly powerful sources: the former being stellar mass (to possibly intermediate-mass) and the latter being supermassive black hole sources. However, lots of underlying physics are still unfounded. For example, the true origin of compact objects in ULXs, particularly in their hard states, is still in question; the true nature of accretion processes in blazars is not well-understood when often they exhibit jets along with optical Keplerian disk components. I will show that strong magnetic fields in the premise of advective accretion disks in general relativity would help to resolve the problem. If the field is super-Eddington away from the black hole but sub-Eddington to its near vicinity, hard state ULXs should even be stellar-mass black holes. On the other hand, our model suggests that while FSRQs are accretion-dominated sources, HSP-BL Lacs are magnetically dominated. Overall, magnetically arrested advective accretion disk flows seem to be the best bet to resolve the wide range of latest data involved with powerful black hole sources.