A Demonic Guardian?

So I'm just going to be blunt and throw it out there. Is it possible for a person's spirit guide/guardian angel to be, well, not so angelic? I get an incredibly dark, powerful, and authoritative vibe from mine and when I asked for his name a few years back, it was demonic.

But here's the thing- he has never harmed me. He has constantly protected me and has even protected my friends and family when I have asked. There have been several accounts where demonic and other evil spirits have tried to wreak havoc on me and my best friend/roommate and he has stepped in and stopped everything (which my friend can vouch for).

For example, one night he would not let me sleep. He kept telling me it was unsafe, that something was wrong and bad things would happen if I let my consciousness slip. I asked that if it was "so bad" that he would help my roommate out too. I thought he was just being a jerk and wouldn't let me sleep because he thought it was fun or something. But sure enough, not 5 minutes later, my friend woke up gasping, wide-eyed and terrified. She told me she was having a horrific nightmare where she was laying in bed and was being attacked by rotting corpse-hands. They were coming at her from all sides like they were trying to take her away. Then she told me that another arm came from behind her but it was different than all of the others- it was a large, muscular human-like arm (that wasn't rotting) with tiger-print tattooed up the forearm. She said it grabbed her shoulder and that's how she was able to wake up.

My jaw pretty much hit the floor. While I had been researching the name my guardian had given me, I came across a reference for tiger-like tattoos and such. And when I felt his presence creep back up into mine he was all smug and pleased with himself- which is really out of the ordinary for him since he is usually so almost regal-like. It actually made me laugh.

And that's just one of the times he has intervened. Any time something bad almost happens, his name basically flashes in my head and everything backs off- as if they would be in some serious trouble if they messed with me. Like I am his. He has always helped and protected and has never done anything harmful to me or anyone I know. But the things that bother me are his name, the fact he doesn't deny he is demonic, and the visions he shows me (which are extremely apocalyptic).

I don't really know why hes with me but he pretty much always has been. I have never delved into the occult, witchcraft, or satanism so I know I didn't bring any of this on myself through any of that. I am not particularly very religious so the idea of having a darker guardian doesn't scare me too much. And I always get the feeling that if he were to leave me I would be in some serious trouble, almost like things are ready to jump me if he backs off.

So ultimately my question is is it possible for a person's spirit guide or guardian angel to be dark or demonic? Has anyone else ever experienced what I am? I know I must sound like a crack addict or something but I have to put this out here and haven't been able to find answers anywhere else.

Thanks for putting up with me!

~Scaleblade