Tweedledoom and Tweedledeath are minor antagonists in Dragon Quest XI.
Before the event of the game, two twins trailmasters turns themselves into these giants and sealed themselves away in Kingsbarrow, waiting for knights to test their camaraderie.
After the rebirth of Calasmos, Hendrik and Sylvando has an argument about what it means to be a knight, their teacher, Don Rodrigo than told the party to go to the deepest part of Kingsbarrow, where they will meet these two golden giants. Tweedledoom and Tweedledeath states that they can only be defeated with combination skills. They than get into a battle. In the end, Hendrik and Sylvando are able to defeat these giants together and finally learns what it means to be a knight.
Tweedledoom and Tweedledeath look exactly the same. They are golden cyclops that holds a large golden mallets as weapon, ready to crush any failed knights.
Dragon Quest I