In an unnamed South American country, Diaz became a revolutionary to overthrow the government. When a freak accident involving a volcano created the Rainbow Creature, Diaz jumped at the chance to claim control over the beast. He used the intimidation factor to help his conquest.
When Batman and Robin came to help the country, they discovered that Diaz did not control the creature and was ultimately as terrified of it as the villagers were. By placing a prism in a house, Batman and Robin were able to scare off Diaz and his troops by making them think the Rainbow Creature was near. What happened to him afterwords is unknown.