Apollo is the Olympian Power of light, prophecy, music, shepherds, and medicine. He helps ripen crops, destroys pests, cures illnesses, and protects shepherds and their flocks. There are many oracular shrines dedicated to Apollo. The master of the lyre and song, Apollo is especially vain about his musical prowess and keeps the Muses as part of his retinue. Apollo is not entirely beneficent, however. He carries a bow with terrible arrows that visit plague and disease upon the targets he fires them at. In his true form, Apollo is a beardless young man who rarely wears clothes.
Apollo is a tolerant, if not forgiving, god. He disdains vengeance, especially killing for vengeance. On the other hand, he encourages strict laws with harsh penalties in order to keep unscrupulous criminals in check. Generally speaking, he is a beneficent god, and there is a small chance that he will send his avatar to aid any beseecher of good alignment who truly needs divine help. On the other hand, he will not hesitate to fire his arrows of plague and disease at any Burg that has fallen into evil and lawless ways. Omens from Apollo are generally delivered through his oracles.
Source: Legends & Lore (2nd ed.)