Heavy Stiltrunner is a pure Sith lord. When he made his oath in the the Sith council he made a pledge to kill all Jedi. When he killed his first Jedi master he just wanted more. His master Reavan said "The power of the dark side shall bring you power and victory." From that moment forward he killed Jedi clones but then he thought of something. He thought that if he somehow told the clones they would be killed after the war they would join him and help! So Heavy killed one clone took his gear told Captain Rex that the clones would be killed after the war and Rex believed him. So Heavy showed Rex that he was a Zabrak and a Sith lord but Rex did not care. Heavy got as many clones as he could and marched them to the Jedi temple. Every Jedi was dead but one... Yoda. Yoda charged at Heavy but Heavy force lightning Yoda so he was stunned. At that time Heavy made his move and stabbed Yoda. After he made a squad called AGE OF WAR ARMY for special Sith and he became the sith emperor and gained more and more power from there...
His Zabrak story
Heavy is a strong, fearless, and cunning Zabrak. He had the strength of for men. Heavy could take down a full grown rancor with just his bare hands . He wanted to be much like his hero Darth Maul. So Heavy got Maul's tattoos on his face to show his power. When Heavy one day was sleeping he could have sworn to hear Darth Maul say, "Heavy! Please help me kill the Jedi Obi-Wan Kenobi!" Heavy agreed to help maul but Heavy at that time had no light saber! So one day he saw a Jedi with two lightsabers walking to a village Heavy decided to to get his knife and kill him. The Jedi turned but it was to late when Heavy stabbed him... Heavy hated having a green lightsaber so he meet a Sith named Darth Reavan and asked him to train Heavy. Reavan taught Heavy everything he knew. So after Heavy's training was complete he found Maul and Savage in a cave. They took Heavy with them and then they found Obi-Wan. Savage got Obi-Wan's attentions so Heavy and Maul made there move and both of them stabbed Obi-wan. Since Obi-wan was dead Maul gave Heavy his lightsaber and then Heavy became a Sith lord.