@FBM,
Hades is the Greek word equivalent of Sheol, which is the common grave of mankind both the righteous and the unrighteousness go there when dead. To have the keys of death and hades is likely a reference to a resurrection from that place. I suppose That might be why the putative Jesus raised the putative lazarus to show that he had power over death.
This is of course assuming scripture to be valid. I could however be very wrong, I have been before