Because they were thirteen and the boy that was always sweet to them asked. By the time they realized it was wrong everything was out of control and when I told Luke I wanted to stop he threatened to tell everyone it was me, he said he would hurt Charlie.

[ luke was charismatic, charming. silena was a teenage girl with a crush and he told her that she would be saving lives. she was a child. luke made her do awful things -- she poisoned thalia's tree and framed chiron at his request -- but losing charlie hurt more than anything else and she gave up fighting luke until she couldn't anymore. ]

He promised me no one would get hurt, but Charlie...

[ her voice cracks and she trails off. ]