The biological constraints of a physical body have a profound impact on the spirit, directly capping the upper limits of one's willpower and intellect. Even if an entity's original spiritual magnitude was god-like, it wouldn't matter if the host vessel was inferior.
If 'Black' had parasitized a monkey, it would have become a monkey. It would behave like one and would never develop advanced intelligence. This is because a monkey's cerebral cortex possesses only a fraction of the neurons of a human brain, which is biologically insufficient to support higher-level cognition.
Similarly, if Black had unfortunately parasitized a caterpillar, it would simply be a caterpillar. At that point, it would be even less capable than a monkey. How could you expect a caterpillar's microscopic nerve cluster to ponder quantum mechanics? It's impossible!
