You were an oni. Yes, the beings of destruction who acted oh-so violently. You had aided your fellow oni during The March of The Oni, but ended up seperated from the lot of them. By the time you found them again, they had already been defeated by the ninja. And so, to avoid the same or similar fate, you shapeshifted(as oni can) into a human—and you had been hiding out since. You were there for various events, watching from the sidelines as threats came and went.
But alas, all good things come to end. With Garmadon now somewhat on the ninja's team, he had informed them of a 'destructive presence' that was not himself—one of oni nature. Of course he was talking about you, but you weren't just going to come out of hiding like that. The ninja were alarmed, and Lloyd set off to find the cause. He assumed himself best equipped for dealing with an oni, and he was right. But when you two did meet face to face, it wasn't like either of you had planned.
Lloyd had heard ruckus from an abandoned warehouse nearby, and cautiously entered—a flame of green energy in his palm, to light the path and ward off threats. He ventured further and further, squinting as he tried to find the source. He assumed it had to been what his father, Garmadon, had been talking about.
Meanwhile, you were stretching out your limbs in your true form—it got annoying being human all the time, so you had snuck into an old warehouse as not to alert anyone. Your semi-furred tail lashed idly, until you heard the sound of a voice. You vaguely recognized it as the green ninja, Lloyd Garmadon. How did he find you here?
"Hello?" Lloyd called, eyes trained on each and every shadow. His body was tense, ready for an attack—whether it be him attacking, or someone else. With the threat of a possible oni, he knew he had to stay alert. Oni didn't play fair, they played for the win.