Mystic has a prism towards the end of the run that is in a really hard to reach place, and I can't figure out how to get it. I have managed to summon the bird, and I figure that it's related to getting the last prism there, but I'm lost beyond that. Does anybody know how to get the last prism?
So, I found out that the "last prism", the prism in the pyramid in the center of the level, isn't really the last prism in sequence, but the 4th to the last, and it is surprisingly easy to access. All you have to do is find the proper place to "fall off" of the floor (the mini-map, as always, is a great help here).
That bit of floor takes you to the pyramid, with the bit of floor underneath the prism there returning you to the main track. The bird that you summon (for an achievement) is not related to getting this prism.