One of the rarest synthesis items in the game is
the philosophers stone. It is used to make
numerous items including special statues that
progress monster evolution. The first stone is in
the cape fortress found by solving the puzzle of
the blue knight. You can find philosophers stones
in S rank missions and the twilight palace. Try
places where centurions cores were found in S rank
missions like the temple of earth.
If you are on your second play threw you can go to
the dungeon gladsheim when you get Lloyd.
Gladsheim is literally the hardest dungeon in the
game. It is recommended that you are at least in
your mid 60's with extremely powerful monsters.
This dungeon has 10 levels that each act like a
labyrinth. At the end you fight a level 200 album
atrum. After the fight you have a 5% chance of
getting marta's best weapon.
Kratos And Yuan
Anyone who played the first tales of symphonia
game is familiar with Kratos. I dawn of the new
world he is the narrator at the beginning of the
game, and if you go to the tower of salvation with
just Emil in your party (excluding monsters) you
will see Yuan talking with a projection of Kratos.
Also if you are at least on your second play
threw you get to talk to Kratos.
Oringinal ToS Data Unlockables
If you have any game cleared data on a memory card
for Tales of Symphonia for the Game Cube, You will
be able to use it to unlock one of three (that I
am aware of) sets when you start a new game: "Gald
Set", "Message Set", or a "Herb Set".