When Glaring Aegis enters the battlefield, tap target creature an opponent controls.
Enchanted creature gets +1/+3.
2/25/2015 If you cast Glaring Aegis, and the creature being targeted by the enchant creature ability becomes an illegal target before Glaring Aegis resolves, Glaring Aegis won’t resolve. It won’t enter the battlefield, and its triggered ability won’t trigger.
2/25/2015 If no opponent controls a creature when Glaring Aegis enters the battlefield, the triggered ability will be removed from the stack and have no effect.