Old, ancient, extremely old. prehistoric.
The Situational Irony that occurred in "The Colomber" by Dino Buzzati was the fact that Stefano gave up his dream of becoming a sea captain to ensure that he will live a long life after seeing the Colomber.
It was believed that the Colomber was a harbinger of Death and that whoever sees it will be doomed for life.
However, the reason why the Colomber was after Stefano was because it was tasked to give Stefano a pearl that will give him good luck and success in life.
It is ironic because the reason Stefano feared the Colomber was false and baseless.
I believe your answer is 1. character versus society. Hope this helped!
Thanks!
~Steve