Euclio is a bit of an old miser. Having stumbled upon the eponymous pot of gold, he jealously guards it instead of putting it to good use. Euclio is so terrified of someone stealing his treasure that the gold brings him no happiness at all and turns out to be more trouble than it's worth. Euclio isn't a bad man by any means, but his obsession with hanging on to his grandfather's pot of gold has turned him into a suspicious, paranoid man incapable of trusting anyone.
It's also made him neglect his responsibilities as a father. He's so preoccupied with preventing his gold from being stolen that he remains oblivious to his daughter Phaedria's pregnancy. Euclio's still blissfully unaware of Phaedria's condition when Megadorus asks him for his daughter's hand in marriage. Once again, wealth has blinded Euclio to what's happening under his very nose. However, Euclio eventually comes to realize that gold isn't everything, thus proving that he's a fundamentally decent man who was temporarily dazzled by wealth, as most people are at some point in their lives.