Board Thread:General Discussion/@comment-26830922-20150829155234/@comment-26830922-20150919134834

If the Soul King's legs are a human and hollow respectively, then they would have to possess powers beyond those allowed to their races. Humans die often and so that leg may take the form of a power that is held by different humans at different times. According to Aizen, Orihime's rejection of matter is an ability beyond that of which humans are allowed, and it has been shown not to be a Fullbring. As for the hollow leg, in Ulquiorra's backstory while he is still a hollow he finds a tree that turns him into an Arrancar. Also, for an arrancar Ulquiorra possessed unusual abilities such as a second release form and he retained high-speed regeneration. The tree in question may have given him these abilities, and it could mean this tree was the Soul King's hollow leg. If this were true, it could explain the unusual bond between Ulquiorra and Orihime.