I can help you...
You would have better luck if you searched for a specific mastiff breed. here are a few: old english mastiff, bull mastiff, roman rottwieler, mastino (neopolitan mastiff), dogue de bordeaux (french mastiff), tibetan mastiff, pyrenean mastiff, and the spanish mastiff. Mastiffs make great guard dogs and most of them will protect you till the death. They are sweet natured, not too hyper, but they can be stuborn with training. They are not dog aggressive(make sure to get one from a responsible breeder!)