Magical artifacts are always a gamble. They tempt us with powers beyond our wildest dreams, but there's always a price to pay.
Just before the great mushroom war cast the world into a post-apocalyptic world of magic and monsters, an antiquarian named Simon Petrikov acquired an ancient golden crown. To wear this artifact was to invite strange visions and lapses of consciousness – but it also gave the wearer chilling magical powers.
Petrikov lost his sanity to the crown and in turn lost his fiancé Betty -- all as the world descended into atomic desolation. While the crown enabled Petrikov's survival and granted him an unnaturally long life, it reduced him to a bumbling, petty and desperately lonely old man. Now known as The Ice King, he dodders away in his fortress with his pet penguins, plotting to kidnap princesses in a demented attempt to reclaim the love he lost in another life.
The lesson: No one wants to be the Ice King. Sure, his powers are pretty dope and the crown sure does look fancy, but his fate serves as a reminder that cursed artifacts are a horrible magical investment. That's why we call them "cursed" magical artifacts and not "entirely reasonable" magical artifacts. They're shortcuts to power at best.