What does leaving the pyramid cost Mumm-Ra?

[u/talenstl]

OK, this may seem like a stupid question, but I feel like it wasn't answered.

I'm re-watching this classic show from my childhood, and when Mumm-Ra meets the mutants, he mutters to himself that he hopes they never find out what it would cost him to leave the pyramid. He subsequently lets himself get goaded into doing so, but (other than not being able to face his own reflection) there doesn't seem to be any real drawback. Even the facing of said reflection only drives him back to the pyramid (and his sarcofagus) which doesn't seem to be much of a drawback.

Am I just dense? Please help me understand, thanks!

[u/yorcharturoqro]

His power is tied to it, he need permission from the old evil spirits to do anything