You control a nontoken creature that can be cast using one colored mana.
Wood Sage does not have summoning sickness.
Steps
Activate Phyrexian Altar by sacrificing the creature that can be cast using one colored mana, adding one mana of any color.
When the creature dies, Mortuary triggers, putting the creature on top of your library.
Activate Wood Sage by tapping it, naming the creature put on top of your library, then revealing the top four cards of your library and putting the creature into your hand.
Cast the creature by paying its mana cost.
When the creature enters the battlefield, Intruder Alarm triggers, untapping all creatures.