All permanents on the battlefield (Arlinn has at least three loyalty counters on it).
Steps
Activate Arlinn's loyalty ability by removing two loyalty counters from it, creating a 2/2 Wolf creature token that enters the battlefield with a +1/+1 counter on it.
Activate Xavier Sal's first ability by tapping it and removing the +1/+1 counter from the Wolf token, creating a copy of the Wolf token that enters the battlefield with a +1/+1 counter on it due to Arlinn.
When the Wolf token enters the battlefield, Intruder Alarm triggers, untapping all creatures.