The pokeball is one of the greatest technologies known to man – the item which did as much as the opposable thumb to make man masters of its planet. The most advanced pokeballs of this era can capture any species on earth except humans, yet depending on which species they seek to capture, they do so with dramatically varying degrees of difficulty. The hardest pokemon to capture, at least among those whose existence can be reliably attested, is Beldum, which is said to be less tameable than the gods.
A Beldum's brain is remarkably skilled at advanced mathematics, and therefore although born in nature has often been compared to a supercomputer; its advanced mind is also the source of its psychic powers. Yet Alakazam are if anything more intelligent, and they are glad to be trained by man, so this alone can not explain Beldum's fierce independence. Some have sought the answer in a Beldum's magnetism interfering with the very structure of pokeballs, yet Magnemite are captured with ease. Others refer to their hand and ball shape – the very release of a pokeball from a trainers hand looks to them like a devastating injury, and unless they are too injured or distracted to notice, they are far too horrified to be captured. The theories are myriad, yet none can be proven, and all have their share of flaws; humans still have not neared the truth.
There are none who have yet learned how to communicate to the Beldum more than attack names and mathematical questions, and thereby learned to ask the Beldum themselves why they are so hard to capture. Yet this very failure may itself hold the answer: the Beldum have no desire to be trained by those who can not even ask them a simple question.