Warcraft Encyclopedia: Gods

There are no hard and fast rules to define what it means to be a god in Warcraft, save that all gods are immortal. Gods can be fundamentally incorporeal, like Elune, or they may have physical bodies.

Gods are neither omniscient nor omnipotent. Take for example the case of the Soulflayer. Many of the trolls in the Gurubashi empire rose up against his bloody rule. They succeeded in destroying his avatar and banishing him from the world of Azeroth. Also, the benevolent titans, though not gods themselves, cast a magical slumber upon the Old Gods and imprisoned them far below the surface of the world.

It is possible for a god to exert influence over several locations simultaneously. Yet the power of a god is limited. Otherwise, of course, the Old Gods could not have been imprisoned. Nonetheless, an imprisoned, sleeping, or otherwise enfeebled god may still have an effect--conscious or not--on the god's surroundings. The development of the qiraji is said to be the result of just such an incidental influence.

Can one ever truly destroy a god, putting a lasting end to its existence? Unfortunately that question has departed the realm of philosophy and become a matter of vital concern. Not long ago, the priests of Hakkar the Soulflayer succeeded in summoning their hungry god physically into Azeroth. Worse, C'Thun has awakened, freed itself, and reemerged from the planet's depths. Many valiant heroes are banding together in the hope of defeating these two evil gods.

References

The information could still retrieved from http://www.wow-europe.com/en/info/encyclopedia/index.xml.