Reincarnated As An Evil Spirit

In a fantasy world of system where modern technology didn't exist and magic reigned supreme. Our protagonist was reincarnated into this world but not as a human or monster heck he wasn't even reincarnated alive. Watch how he who has become a little spirit which can posses other creatures body and alter them into something monstrous to further strengthen himself. See how the little spirit turns into something demonic which the mortals and gods alike learn to fear. Even if a dragon burns him or a giant steps on him, he could always find a new body or even posses the dragon or giant themselves. >:] Note: The mc will openly embrace his dark side and won't hesitate to take innocent lives if its necessary to achieve his goals.