Commune

Commune was a divination spell that allowed a priest to ask yes or no questions of his or her deity.

Effects
By means of this spell, the caster was put in contact with his or her deity, either directly or through a proxy, agent, or servant. The priest was allowed to ask one question per experience level and could expect a truthful yes or no answer based on the entity's knowledge at the time. Note that even greater deities were not necessarily omniscient, so answers such as "I don't know" or "unclear" were possible. If a yes or no answer would be ambiguous, the entity could choose to elaborate with a few more words if it served their purpose. If the caster's attention wavered between questions, the spell was ended.

The post sundering version allowed three questions regardless of level and if a one word answer would be misleading the answer could be a short phrase. if cast several times before a long rest it becomes about 25% more unlikely to get a answer.

Components
In addition to verbal and somatic components, this spell required the use of the caster's holy symbol or divine focus, some (un)holy water, and burning incense. The newer version of this spell also exacted a price of a small amount of life experience.

Trivia
A servant of the Fallen, a cleric of a dead god, couldn't cast the commune spell.