You control another nontoken nonartifact creature.
Steps
Activate Ashnod's Altar by sacrificing another nontoken nonartifact creature, adding ({C} magic symbol) ({C} magic symbol) .
When the creature dies, Missy's first ability triggers, returning the creature from your graveyard to the battlefield face down as a 2/2 Cyberman artifact creature.
When the creature enters the battlefield, Intruder Alarm triggers, untapping all creatures.
Activate Skirk Alarmist by tapping it, turning the creature face up.