Defeat Alexei at Zaude.
EDIT: Go a little more in-depth here. Depending on your games difficulty, Alexei will use his moves more or less often and they will be much stronger or weaker. Being around level 45 - 50 is wise (I was around that area, maybe a little higher). Each gamer has his or her own preferences, but my party consisted of Yuri (raw attack), Raven (long range + support), Judith (raw attack) and Estelle (support). One may switch Raven for Repede or Karol, I wouldn't suggest having Rita in the party just because of the time it takes to cast spells and they may miss if it doesn't cover the entire area.
While you're at it, grab:
You'll get a slightly different scene, and it's just way cooler.