There's Inner Beast, Inner Darkness, The Inner Dragon, The Void, The 7th Chakra Gate... Each one is a slightly different thing. The Darkness is everything you desire to be, but hold back. The Inner Beast in the wild animal aspect. The Dragon is a craving of absolute power and comes from that which you draw power from, The void is the call of demons and the power to annihilate everything, and then the 7th Chakra is an attunement to the aetherial powers throughout the world. Similarly, one could argue attuning to the constellations also falls in this category of things. Each one will destroy you in a different way though.

If you're overtaken by Darkness, you would become evil. Overcome by the beast, you become a marauding animal. Overcome by the Dragon, you become a thrall of Nidhogg. If you are overcome by the void, Demons take possession.