Complex sentence: An old man (Odin in disguise) advises Sigurd on choice of horse, and in this way Sigurd gets Grani, a horse derived from Odin's own Sleipnir.
Split into simpler sentences: An old man (Odin in disguise) advises Sigurd on choice of horse. In this way Sigurd acquires Grani, a horse derived from Odin's own Sleipnir.