1. Register someone's ( or more ) friend code on your DS.
2. Send 7 messages to another DS ( faraway or nearby )
3. Send messages to Takka until you get a reply talking about Orichalum.
4. Fix Sara's pendant by sending messages until you get a reply saying that her pendant is broken.
5. Ask Takka to fix it
6. If that doesn't work, go meet the legendary smith. Leave the floating continent and go to northwestern Saronia City. The legendary smith should be near the path leading to the library. If you find the Orichalium (Used to make a Ultima Weapon), she will forge something out of it and give it to you in return for finding the Orichalum 7. Get it fixed and return it to Sara.
8. Send messages to Cid until he replies with a "Something is in the basment.." kind of title.
9. Head to Cid's house in Cannan and talk to Cid. Head down to the basement on the east side of the room, kill Aeon and it should drop Unknown Metal. Talk to Cid and he'll say that it is the legendary metal called, Orihalcum.
10. Do not go to Saronia. Go to Falgbard (City with all the Dark Knights). She should be beside the river in town, so go talk to her and will take your Orichalum and forge it into a weapon called the Ultima Weapon.