There is not much known about the origins of Satanine, where it came from or how it came to be, let alone why it is a dog/cat like creature. I’m not sure if Satanine itself is aware that it is the ruler of Hell as it does not act inherently evil, and being that it is in Hell surrounded by evil beings and entities, it is presumed that it is merely going with what it thinks is the norm which is to bestow evil, not be evil. In other words, playing a part that was adopted from its environment (hell). This notion may actually be worst than if it were truly evil as Satanine does not believe its actions and effects it has on other beings is bad or evil which means it lacks total empathy for anything. Screaming, crying and pleading for ones life would fall on, not deaf, but indifferent ears as he may not be able to differentiate between satisfaction and pain. An evil being or entity at least knows what they are doing is evil and is affecting others in a negative way where Satanine wouldn’t be able to recognize the effects of his actions were having a negative impact on others. All he would do would be to continue hopping around adorably like a cute little puppy or kitten. 

While Satanine will beg and pester you for treats and whatever else he wants until you die, he himself is immune to begging, pleading, or bargaining, especially when done so for the sparing of ones life. If you plead or beg for your life to Satanine, he may share one of his treats or toys with you thinking that’s what you want from him as that is all he would want from you. Satanine’s toys and treats have adverse effects on anyone beside him, mind you. Sometimes it may seem like Satanine is acting out some kind of plan, but really, he isn’t. He’s literally being a creature that happens to have access to powerful, hellish powers.