You control a nontoken creature that can be cast using ({C} magic symbol) ({C} magic symbol) .
Wood Sage does not have summoning sickness.
Steps
Activate Ashnod's Altar by sacrificing the creature that can be cast using ({C} magic symbol) ({C} magic symbol) , adding ({C} magic symbol) ({C} magic symbol) .
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.
Repeat.
If the creature can be cast using ({C} magic symbol) or less, this combo nets infinite colorless mana.