Summary by @tldr:

A few infant souls had sustained him for two hundred years, but that type of transplant wasn't easy to perform, and now the very force that had allowed him to cheat death and retribution for so long had dried up and turned against him, ravaging his body more extensively than any cancer.
Transplanted organs and infant souls and the thousands of other acts that he had performed gladly in exchange for his long life were now buying him less and less time; Some of what he'd done had given him wealth and power.
All his bloody work would finally start to yield him dividends, and he wouldn't have to worry about transplanting organs or snatching souls for the foreseeable future which he hoped to count in centuries.
He'd woven wards around this stolen house that would burn anyone who tried to cross them to cinders before they knew what was happening, so even if the American Police traced the disappearance of this girl to him, which was about as likely as Arthur returning from Avalon, he'd have the time he needed to collect his prize and move on.
In earlier times he hadn't needed to eat, his magic used to make food irrelevant, but placing that much trust in it now would be idiocy.
One drop of his power escaped and before he had time to think the wall to his right evaporated, one of the thick oaken beams above him split down the middle.
The sound of their torment almost produced an instinctual recoiling, when any sudden action, physical or mental would give him that glorious crater he'd wanted a minute ago.