I see that the Dynamix games don't receive much attention here. Anyway, I have this question and I hope someone knows the answer. Oh, of course this might give spoilers, so don't bother reading this if you haven't played the game.
Ok, I have finished and explored the game many many times, and explored even "wrong" or alternative ways to some puzzles. Still, the most puzzling items to me is the "Tome of Knowledge" and the "Rock of Life" the Old Man gives you. I haven't ever found a use for them.
The only "usage" of the Rock I have found it that you can give it to Karyn. She will think that it's a gift and keep it. But then, Blade thinks "I hope I won't need it later" making me wonder whether the game intends a use of it sometime later. Giving the Rock to Karyn doesn't alter her behavior anyhow (eg. making her more friendly), but keeping the Rock didn't help me in a puzzle either.
A walkthrough I found says that these two items are Red Herrings. I guess it is so, but this comment by Jake that he might "need it later", makes me suspect that it can trigger a little-known alternative solution to a puzzle.
Anybody knows more?