The second crown, referred to as Coronam Mortis, is a simple iron-band-type crown, rust-eaten and bent, similar in style to the Deal Warrior Crown. On it's base is apparently a Norse Toten-Rune.
Legend holds that they were possessed by a cult of pre-Druidic sorcerers, who used them to attain eternal, yet infernal, life. The details of the repellant ritual are forgotten among civilized men, but with it's completion, the sorcerer, wearing the Gold crown, would force his mind into the body of a younger person, wearing the Iron crown. The sorcerers old body would then be killed, along with the young victim's mind residing in it. In this way, the sorcerers would leap from body to body, generation after generation. Legends even detail sorcerers using this method to inhabit the bodies of animals and there are even hints to more exotic types of victims.
Brozek relates the history of the crowns as the Dominicans reported to him. The Order had originally acquired the crowns, for a very reasonable price, from a Jewish moneylender in the 14th century. The moneylender had himself only recently collected them from the estate of the unfortunate, and rather disreputable Duke Frederick of the House of Metzengerstein, after the abrupt passing of the Duke and all his known kin.
It is unclear, how the crowns came into the Duke's possession, but judging by his families evil reputation for dabbling(and more than dabbling) in the occult, it is not surprising that such an artifact would end up in his collection. In fact, before their untimely demise, the House of Metzengerstein had quite an extravagant reputation for queerness, and the local peasantry would whisper that they were to blame for the occasional disappearance of their children.
Given the evil reputation of the crowns and their former owner, the Dominicans were happy to acquire the artifacts, thus ridding the world of their unholy influence. They first attempted to melt them down, but they were protected by powerful pagan magicks. As such, the Order was content to shut them away safely in the monastery's vaults.
The crowns remained safely forgotten until the early 17th century, when a self-proclaimed heir to House Metzengerstein appeared with his servants at the doors of the monastery, requesting to buy-back the crowns in an attempt to repurchase his family's lost heirlooms. His appeals were rejected by the stalwart monks, but he later returned with a Royal Directive to allow him to repurchase the crowns for a fair price.
Not wanting to release this ancient evil again upon the world, the monks called for advice from the renowned Jan Brozek from the Krakow Academy. Jan relates his plan, that the a replica quickly be commissioned of the Coronam Mortis. The replica, as well as the original Coronam Vitae, which could not be so easily duplicated, were sold to the heir of Metzengerstein. The original Coronam Mortis, was secreted away to a more secure location, in case the forgery should be discovered and a royal order be made to search the monastery. Brozek doesn't recount where the crown was moved to, but he assures the reader that:
"I was accompanied by a dozen stout-hearted monks on the most harrowing journey of my life. It took all of our faith and courage to survive the ordeal, though ten of our number truly did not survive in body. The thing is surely safe now, beyond the realm of mortal man, and their petty, sinful aspirations. Indeed, it's new protectors know no fear of man, and bow to no Human liege."
However scholars suspect that this record is a screen to set searchers for the crown on the wrong track. Rather, they suspect that the crown is still hidden in the vicinity of the Old Town of Sandomierz. This is supported by the records showing that Brozek could only have been in Sandomierz for a few days, and by his party having been waylaid and searched in vain by the Metzengersteiners upon leaving the town, by his own account.