MdZ-BLK, nicknamed Blockhead, was a MdZ Maintenance Droid.
Mdz-BLK was owned by the Seville pirate clan and Darion Seville, the matriarch of the clan, liked to arranged duels between her droids. During these contests, MdZ-BLK regularly fought against protocol droids, winning every time. However, on one occasion, he had finally had enough of fighting, so leapt out of the fighting pit and attempted to kill Darion Seville. Her son, Yearo Seville, saved Darion by ionizing MdZ-BLK and then had him delivered to Gorbu Dalo, a Hutt pirate who was a rival of the Sevilles. Yearo hoped that MdZ-BLK would develop enough hatred for Dalo that he would attempt to kill him. Seville was correct in his prediction and Mdz-BLK killed the Hutt. He then tried to gain revenge against the Sevilles, by programming some protocol droids to steal a freighter from a family of Duros. After converting the freighter into a giant bomb, they flew it into an asteroid where the Sevilles were based, killing many of the pirates.
Afterwards, MdZ-BLK joined the Alliance to Restore the Republic and became the partner of the Human Aimi Loto. Together, they traveled the galaxy, carrying out acts of sabotage against the Galactic Empire. They programmed some droids to disrupt the wedding of the daughter of Moff Nile Owen and later traveled to Kwenn Space Station.