Idle units heal much faster than those moving or engaged in combat. Some units, such as undead, Titans, or the dragon, Nidhogg, cannot be healed.

Apollo was the father of Asclepius, the god of medicine, whose symbol, the cadeuses, is still used as a symbol for medicine today (though is often portrayed as the winged staff of Hermes's, not the serpent-entwined staff of Asclepius).

"I begin to sing of Asclepius, son of Apollo and healer of sicknesses. In the Dotian plain fair Koronis, daughter of King Phlegyas, bare him, a great joy to men, a soother of cruel pangs. and so hail to you, lord: in my song I make my prayer to thee!"

--Homeric Hymn XVI