Whenever I manage to achieve my first lucid dream, I want one of my first things to test out to be summoning a massive army. But, can your brain support this giant amount of "data"?

For example: Is it possible for me to close my eyes (or open a door if that works too) and open then with the thought: "I will become Maximus Decimus Meridius, leader of the North Roman legion. I will stand before my 10,000 troops." Will such a thing work? Will the army be there when I open my eyes? Or is this too much for the brain to process?

So, in summary: is there a limit to DCs?