Shortly after unsealing the tomb of Polish King Casimir IV Jagiellon in 1973, ten researchers mysteriously died. The true culprit was likely a massive concentration of fungal spores festering inside the sealed tomb, which proved fatal when inhaled. Related Story After You Die, A Universe Eats Your BodyFuneral practices at the time of the king’s death contributed greatly to the growth of the deadly fungal spores. King Casimir IV Jagiellon , born in 1427, first became the Grand Duke of Lithuania in 1440 and then the King of Poland in 1447. When researchers opened the tomb nearly 500 years later on April 13, 1973, the coffin had rotted away.