这句话后半截我一直没明白,求解The river runs right out of it through the gr

这句话后半截我一直没明白,求解
The river runs right out of it through the great cliff at the South of the Mountain, and out of it comes the dragon too-far too often,unless he has changed.
求解“ and out of it comes the dragon too-far too often” 这句怎么去理解.出自霍比特人.
"We might go from there up along the River Running," went on Thorin taking
no notice, "and so to the ruins of Dale-the old town in the valley there, under the
shadow of the Mountain. But we none of us liked the idea of the Front Gate. The
river runs right out of it through the great cliff at the South of the Mountain, and
out of it comes the dragon too-far too often, unless he has changed."
这是整段