What is in this image? Describe it as if you were explaining it to someone from the 15th century.

This illustration, akin to a parchment sketch, captures a most fantastical creature. It is a large, heavy-set beast with a back adorned by pointed spikes, like that of a fearsome saw blade. This creature has a tail, four solid legs resembling that of a sturdy tree trunk, and its hide is speckled with circles and ovals, as if painted by the heavens. Its maw lies open towards a smaller creature, standing upon two tree stumps, which is either emitting something from its mouth or consuming something invisible—a trick of the artist, perhaps.This smaller beast, no less strange, has a pointed, elongated snout and wide, staring eyes that exude an air of both fright and curiosity. The setting around them is simple an open plain sketched lightly with faint clouds dotting the sky, suggesting an idyllic landscape. Such an image stirs the imagination, presenting creatures from a world possibly untouched by time, or sprung from the vivid dreams of a visionary artist.