All drawings of the stage are batched and rendered by a SpriteBatch renderer. So when the Draw event of an actor is triggered, SpriteBatch.Begin has already been called by the stage, and SpriteBatch.End will be called automatically after the last Draw event. If you call the Render function of a MapRenderer in a Draw event, you get the error message above ("SpriteBatch.end must be called before begin") because the MapRenderer, which is a renderer like the Spritebatch object of your stage, calls its own Begin function to start its batching process.