Doctor Robotnik is a fun one to throw into those "what would [media character X] do with [cursed artifact Y]" hypotheticals because the answer is always "misunderstand or disregard its intended purpose and use it to power a giant evil robot". The One Ring, the Death Note, the Necronomicon – it doesn't matter. Evil robot. The question isn't what he'd do with it, but how it's going to go horribly wrong.
Thanks! You just gave me at least three ideas for Sonic fics! Granted, not fully-formed, but I can flesh out the details later.