3 0 0To unlock this trophy you must find the mysterious creature in the Temple chapter (this is the chapter just after the underground section where you must avoid the guardians).In order to find the mysterious creature you must activate all of the story related glyphs (the glyphs that raise the level of the mist). Once all glyphs are activated, fly back down to the bottom and the creature can be found in one of the openings of the center tower. Hold circle so you "activate" the creature and the trophy should pop.
0 0 0Following on from dehersh's solution, here is a video showing it (and also one of the hidden symbol locations)Hope this helps