Second Shadow wasn't a loyal follower of the Demon Lord, but he wasn't a fool either. So, fighting against Elyra or killing Serene, were the two options that he considered as safe, when comparing to the possibility of having Velgor's anger directed at him. The other members of the Twelve Shadows may not have realized, but his instincts as a top-notch assassin, told him that there was something really wrong with his master at that time.
Now that Serene and Yuyin had escaped though, he was left with the only other option. To fight against that elf.
But since he just wanted to waste time, he didn't move even after a lot of time had passed. His plans were to use this fight as a fake cover, until the other members were able to finish the job.
