and as soon as the lad did what the horse said, up rose a great black hill of rock behind him. so the troll had to be off home to fetch something to mine his way through the rock; and while the troll did that, the lad rode a good bit further on. but still the horse begged him to look behind him, and then he saw a troop like a whole army behind him, and they glistened in the sunbeams.