I was unable to post yesterday, which is why you get two writing glitches today.
Around the world, various hell gates are opening. Demons are pouring out of them, wounded. Satan himself appears on television, saying, “Something has invaded Hell. Humanity, we need your help!”
You don’t necessarily have to leave hell uncapitalized in the first instance (hell gates), but you do need to capitalize it in the second, because it’s definitely a proper noun there.
You could leave out the word saying, but then you’d need to use a period instead of a comma before the dialogue, because appears on television is an associated action (beat), not a tag.