Euclio is above all a character who is defined by his greed and avaricious nature. It is clear from the very opening scene, when he beats Staphyla, his old slave who is very loyal to him, that his greed is possessing him, and, above all, the pot of gold that he is so delighted about having, is beginning to own him rather than the other way round. Note, for example, what he says in an aside whilst beating Staphyla:
Oh, but how horribly scared I am she'll come some sly dodge on me when I'm not expecting it, and smell out the place where the gold is hidden. She has eyes in the very back of her head, the hellcat. Now I'll just go see if the gold is where I hid it. Dear,dear, it worries the life out of me!
In particular, the last phrase, "it worries the life out of me!", could be used to show the major theme of this play: the dangers of greed and the way that possession of wealth does not necessarily come as a blessing to its recipients. Euclio's greed is shown to affect every single part of his thoughts, as when Megadorus generously proposed marriage to his daughter, he automatically suspects that Megadorus must have found out about his wealth and wants to marry his daughter in order to get it. Even when he has agreed to the marriage, and he finds his house full of people getting ready for the wedding, he is so obsessed with his gold that he automatically assumes they are looking for his hidden pot of gold. Euclio is therefore a sadly comic character who takes his love of the pot of gold to extreme lengths, showing the negatives of greed.