I'm guessing it's your turn if they're able to play
Nemesis Trap
, seeing as it has to target an
attacking creature - which
Angel of Despair
is only going to be on your turn. ^^
1. They do get to destroy a permanent. The token is a copy of
Angel of Despair
, complete with "when Angel of Despair enters the battlefield, destroy target permanent" - which triggers when the token enters the battlefield.
2. The copy is
exiled at the beginning of the next end step - which will be your end step, seeing as the next end step to occur after your combat phase is your own end step.