You control at least one nonlegendary creature token.
There is at least one counter on a permanent you control.
Steps
Activate Xavier Sal's first ability by removing a counter from a permanent you control, creating a copy of a creature token you control that enters the battlefield with at least one +1/+1 counter on it due to Arwen.
When the creature token enters the battlefield, Intruder Alarm triggers, untapping all creatures.