Yoga

Is yoga energetically good, neutral or does it open us up to dark entities?  I've heard some eastern religions speak about how yoga is really like a form of witchcraft and that the poses open up your body to demons or dark energy.  Which intuitively seems so opposite of what everyone gets out of it, which is connection to body, mind, soul.  Just curious if there is any sort of history to yoga practice or things we should be mindful of.