Google is not a big help here. I remember an anime series with a fighting robot. Two specifics stood out in my mind. (Which hopefully doesn't indicate my remembering two different series)
1) The boy who controlled the robot did so by phasing through the rock of a mountain that the robot was in.
2) The bad/guy witch had a face that would split apart down the centre. I think it revealed a smaller version of the bad guy/witch when it opened.
My guess is going to be late 70's early 80s. It was on US Broadcast TV. So likely it was dubbed into English.