Hmm, since you can't remember where the Rapax Prince battle was...Then back to the statues. Look at the fountain with the three statues. Follow where the Trynnie statue is pointing (northwest). Note that part of this way is also the way to the dumping point for the Destinae Dominus. But if you've gone back to that dumping point (the temple), then you've gone too far. The Rapax Prince battle was at the first large clearing you reach following this path. In this clearing, look at your map, and take an eastern path. Once again, if you end up at the place where you dumped off the Destinae Dominus, you took the wrong path. There was a branch off. If you've placed all three items, then by the time you reach the stairway, something should happen. If you haven't placed all three items, nothing happens, and you can't climb the stairway anyways.
Good luck.