Primal Mistborn

The beads of metal found at the Well—beads that made men into Mistborn—were the reason why Allomancers used to be more powerful. Those first Mistborn were as Elend Venture became—possessing a primal power, which was then passed down through the lines of the nobility, weakening a bit with each generation.
The Lord Ruler was one of these ancient Allomancers, his power pure and unadulterated by time and breeding. That is part of why he was so mighty compared to other Mistborn—though, admittedly, his ability to mix Feruchemy and Allomancy was what produced many of his most spectacular abilities. Still, it is interesting to me that one of his "divine" powers—his essential Allomantic strength—was something every one of the original nine Allomancers possessed.

The Hero of Ages Chapter 22 epigraph