Before Seiken Densetsu 3Edit
The primary reason this is because he was rejected by the human race. Also, both Kevin and Karl share a similar trait with each other: neither of them had a mother growing up. Kevin had found Karl as a baby with no mother one day and the two were friends ever since.
During Seiken Densetsu 3Edit
One day, though, Karl betrays Kevin. This happened when Karl and Kevin get to a certain part of the woods they travel by nightfall, this is where Karl's fate had taken place. In other words, Karl had suddenly growled at Kevin and attacked. Kevin, at first, couldn't bring himself to hurt Karl because Karl was his best friend, so he took the blow from Karl's attacks. When Kevin's HP was reduced to zero, he finally became a wolf somewhat like Karl, and he attacked Karl without mercy. When Kevin finally kills Karl out of self-defense, he reverts to his regular form, and sees his newly-dead friend.
Kevin's heart was broken because he had lost his friend. He buried Karl at the starting point of Kevin's adventure, and made his way to the castle. After Karl's death, this is when Kevin realizes his power. After awhile, it is realized that both the Deathjester and Beast King were behind Karl's sudden attack, so Kevin tried to battle the duo himself, only to take a huge amount of damage from the Beast King's counterattack, flung to Karl's grave, and be left with 1 HP.
Kevin then exiles himself from his Beastmen folk, and encountered the Deathjester again, who had recently left as the Beast King had no more use for him, whom Kevin was more than ready to be rid of. However, the eater of souls begged for Kevin's mercy, which he got in exchange for telling Kevin there maybe hope yet: if Kevin consorts with the Priest of Light in the Holy City Wendel, then it looks promising that Karl could be revived from Kevin's unintended slaughtering. Kevin then begins his journey from this point onward.
The Truth Behind Karl's DeathEdit
Only if Kevin is chosen by the player as their main character or party member, it is later revealed that Karl's death was merely a hoax. When Kevin (and with two out of five other people) returns to the castle, The Deathjester tells Kevin he went on this quest for nothing; that Karl could never be returned to life. Having realized the truth, Kevin tries to attack, but is blocked by his rival, Lugar.
After Lugar is defeated by Kevin, and revived by Luna via turning Lugar into a infant Beastman, Kevin and his friends meet the Beast King. Before Kevin can exact revenge on his father for Karl's death, the Beast King calls Kevin's anger undisciplined and reveals a surprise: Karl is actually alive and well. It is revealed that the Karl at the beginning was merely a fake, but Kevin had failed to catch on to that. In retrospect, the King then tells Kevin that the journey made him stronger.
- Karl's role is similar to that of Eagle, Hawkeye's best friend: both attack their friends due to the antagonists' actions and both are mortally wounded by their friends.
- The difference, however, is that Kevin was not in trouble for killing the mirage Karl, and Hawkeye was blamed for Eagle's death. To differentiate them further, Karl dies from injuries right afterward, and Eagle was slain by Isabella (Bigieu).