Arnold was just messing with Nilerea when he said he would kill everyone on the planet. He had no intention of doing something like that. He just mentioned those things to push Nilerea into doing what she did. If he hadn't pressurized her, he was sure she wouldn't have laid a finger on any one of them.
Arnold spared a look at the severed head before kicking it towards Yan, who understood what the master wanted and resurrected the elven queen as a common soldier. The rest of the captured elves learned their lesson and decided to keep their emotions to themselves. None of them even dared to look Arnold or anyone on his side, in the eye, as they were afraid they will meet a similar end soon.
But Arnold was not having it. He wanted to enter the next phase of his plan as soon as possible. He squatted down to be at the elves level and asked them one simple question.