Like most of the Mormon cult's practices, magic underwear seems to be another poorly kept, weirdo secret.
Their magic underwear are worn under their real underwear. Picture a woman wearing a man's T-shirt and boxer briefs under her bra and panties, and that's the look.
They even sew embroidered patches into their magic undies, adding even more mystical, magical gibberish to the mix.
I had a boss who was a Mormon priesthood holder on the side. You could see the outline of his magic underwear on his upper legs through his trousers.
He professed to be some kind of moral role model but in actuality all he worshipped was money. He treated his staff like slaves and his upper management (all women) like sister wives.
In addition to thinking his magic drawers would bring him x-ray vision, the ability to fly and other insane delusions, he also thinks when he dies he'll inherit his own planet to rule.
He hides behind a conservative, family values, religious Christian Republican facade, but in reality the man is totally batshit crazy.