Fortune is the official name for the law that grants immunity to all weapon and magic damage, along with immunity to all status ailments in Final Fantasy Tactics Advance. It does not provide any attack or magic power boosts.
Fortune is only granted to one character in the game: Llednar Twem. It is granted upon him by Queen Remedi after being created. During the few engagements before the final battle, Marche Radiuju and his fellow clan members will be unable to fight Llednar.
However, during the first engagement at Delia Dunes' Totema Shrine, Llednar is thwarted by Judgemaster Cid who imposes an Advanced Law to prevent Llednar from using his expert skill Omega. However, after only two turns, Llednar becomes overconfident and charges up an Omega attack. Because of this, Judgemaster Cid penalizes Llednar with a Red Card and removes him from battle, effectively ending the current engagement.
During the second encounter at Bervenia Palace, Llednar and Marche face off in Prince Mewt's throne room. Because Marche is still unable to attack Llednar, he must survive long enough for Judgemaster Cid to arrive and scare Llednar off.
Fortune is eventually removed from Llednar via Judgemaster Cid's use of an Antilaw Card. Afterward, Llednar is vulnerable to damage by Marche and his clanners in the final battle, #024 Royal Valley.