This is one of the more interesting, practically unfounded symptoms of Bipolar disorder. It appears fantasy-based upon hearing the individual talk. Even the most devout, avid religious individual will pick up on the non-reality based nature to which they speak.
It may be a form of escape from the tortuous, tumultuous existence they press through, or simply a byproduct of disorganized, chaotic neurochemistry and hormones. It comes across, for instance, as the individual speaking about their personal relationship with some form of God, but in a way that no one else seems to be able to relate to.
Also, they may believe themselves to be the next great savior of the world. It is very extreme and quite noticeable. Its all-to-familiar, final characterizing trait is that they will fluctuate from this extreme, hyper-religiosity to having total complete ambivalence to it weeks later.