Stealthbane was genuinely loyal to Eric because the latter had defeated him with sheer strength. However, he was extremely dangerous and treacherous toward others, especially his enemies.
Back when he escaped from Erweston, several legends had surrounded him. He had managed to injure a few and still escape unscathed, which was a testament to his formidable skills.
Now, in a one-on-one duel, he had the upper hand.
He had no regard for honor or fair play, unlike the chivalrous tales. His method