Tiresias is a significant character in Oedipus Rex as well as Antigone by Sophocles. He is a blind prophet who, ironically, "sees" more than any of the major characters in either play.
In Antigone, Tiresias not only sees the future but he seems to have some inside information from Apollo. Unfortunately, what he can see is usually bad news for the one who calls him in for advice, so it is common for the prophet not to be believed. (Who wants to believe gloom and doom about your fate and future, after all?)
In Oedipus Rex, Oedipus falsely accused Tiresias of being part of a plot with Creon to take over the country; in another great irony, Tiresias is now accused by Creon of having been bribed to tell untruths. Again, who wants to believe such painful and unflattering things. He tells Creon, just as he told Oedipus, that he was going to suffer because of his excessive pride:
All men make mistakes, but a good man yields when he knows his course is wrong, and repairs the evil. The only crime is pride.
Tiresias tells Creon that nature is rebelling against Creon for two reasons. First, Creon has angered the gods by refusing to allow his nephew to be properly buried. Second, he has angered the gods because he has put his young niece, Antigone, in a tomb for her disobedience. Creon stubbornly refuses to believe what he hears, and we are not surprised, as Creon has demonstrated his prideful stubbornness throughout this play.
The last thing Tiresias tells Creon before the prophet leaves is that Creon's family is going to be decimated because of Creon's sacrilegious behaviors. Creon does finally take some action to avert the disasters Tiresias predicted; however, he is too late and loses everyone who matters most to him.