Fifteen years before the start of the series, he fought Dark Schneider in a battle that lasted for several days. Dark Schneider had already succeeded in conquering most of earth at that time and would only need to get a few more kingdoms to rule the entire world. Lars found himself losing the battle and didn't spot any chance of victory. Having no other choice, he summons the "Dragon Knight", a mechanical robot that towers over 500 meters and was original made by the Twelve Wise Men of Europa. The dragon itself, absorbing and multiplying the spiritual energy of anyone who used it, proved useful and helped Lars to kill Dark Schneider. The Dragon Knight itself however was cursed, as it was meant to be used against Anthrax, not Dark Schneider, who was intended to be the ultimate wielder of the armor, and the curse transformed Lars into a baby dragon. After the death of Dark Schneider, Lars is said to have gone missing, or even died, as no one knew what truly occurred on that day.

In the form of a baby dragon, Lars spends his time looking for a successor to the Dragon Knight. He was eventually found by Gara, the ninja master and one of the "Four Lords of Havoc" and made to be his pet. He even follows Dark Schneider around to observe him, knowing full and well that they were once deadly enemies.

His name is likely a reference to Lars Ulrich, the drummer of famous metal band ''Metallica''

(Source: Bastard!! Wiki)