The guru is not a place or a time or a person, but an eternal spirit of true consciousness that arises as that. It is the key to awakening; the reflex of unbinding that is the essence of liberation. That which is created goes into a bound condition, and it is the guru that absorbs that which is created back into its original nature.
The end result of the meeting of the guru and the disciple is the dissolution of separateness between the two. The disciple absorbs the nature of the guru, the guru absorbs the nature of the disciple, and they become one thing.
Even in the cases of the incarnation of the most profoundly enlightened beings, contact with the guru principle is required in order for them to gain access to their latent enlightenment. The guru-disciple relationship is a primal role in the play of creation.