The Pardoner tale tells a story of greed, something the pardoner is all too familiar with. In his tale, three friends go seek out Death with a plot for vengeance. In their search for Death, they come across what they think, is an old man. He informs them to up the road where Death lays. The mystery, who is that old man is supposed to represent? I believe the true answer is the most obvious one, death.
These friends go and seek out a physical being whom they wish to confront and kill. When coming across the old man, the three never realized their chance; death presented himself there, face to face. Death was fair to appear to the trio, but because they never realized who the old man actually was, they lost their one and only opportunity. After falling into Death's trap, no sooner was their fate sealed. Death had leaded them right into gold, and because he knew what greed leads to, the three clashed with Death and lost the battle.
Indeed, it was a little foolish of the group to think they could outsmart Death. Even when given the chance they needed, they were thoughtless and are unable to make the connection. The pardoner tells this tale because he wants greedy people to recognize that greed may eventually lead them to death. It is known that Death is full of tricks and easily deceives, so indeed the old man was death temping the three friends with greed. .