"...I will force you to work for my pack!"
Rex's eyes glistened with purple energy from the King Mark as he declared that he was going to make the prideful Arnulf one of his pack members, it should be a heavy penalty worst than death for someone as prideful as Arnulf.
Anyone that lived a life as long as Arnulf will inevitably develop a huge ego.
Surviving countless battles that can even shred a normal Werewolf into little pieces is surely an achievement in itself, and it was shown clearly by how Arnulf acted despite the Dark Prince beside him before.
Sure, he's at the rank still lower than the Dark Prince, Zegrath.
But how he's leading Zegrath and the other Werewolves he brought, coupled with the way he fought with an insurmountable amount of pride shows the arrogance he developed through the years of his life.
While declaring the words Rex said earlier, he emphasizes the word 'For'.