For your party you will want a Wavemaster like Elk, Wiseman, etc. You also need a heavy Blade Slinger.
Game Over Bonuses (Japanese version Only)
Finish the game one time to get parody mode
How to beat Mia
When you reach the end of the dungeon of Sigma: Graceful Tempting Fallen Angel, you should see Elk and Mia. Mia says she exists only in The World and to forgive her, that she cannot control or hold herself back. She transforms into a huge beast and kills Elk. Threes no where to run. You must kill your friend. Mia begins with 0 HP, just like Skieth, Gorre, etc. Kite and his party should be level 80 or higher (I was on 95, but I'm obsessed with this game). You can pretty much just walk up to Mia and slash her apart, meaning she seems like a breath of fresh air after Gorre, but thats only a front. Mia can cast devastating Element Spells and Confuse a Party member. Her first strong spell is Love Sprite,an area spell inflicting around 900 to 1100 damage(love hurts). Mia has 2 other spells that can completely and utterly crush you. one is Data Drain. It afflicts a character with all 9 status changes and inflicts between 1300 and 1500 damage(ouch). The second one is possibly the most devastating spell of any RPG I've ever played(And I've played a lot of RPG's). When Suspicious Seduction is cast, THE ENTIRE PARTY BECOMES CHARMED!!! The paty will beat the crap out of each other until only one is standing(Probably Balmung). Mia will probably then Cast Data Drain and Love Sprite to finish him off. The only way around this is to use First Aid When Suspicious Seduction is cast. The party will still fight, but as soon as its over, the last one standing should resurrect one dead guy, then he can resurrect the other one, and you can chase Mia down before the third member dies. Eventually, Mia will reach Protect Break and you can cast Data Drain on her. After Drain, Mia has approximately 6000 HP. She can no longer cast Love Sprite, Data Drain, or Suspicious Seduction at this point, but she still can Confuse and use normal spells and physical attacks. Continue to attack her until her HP reaches zero. Goodbye, old friend...
Orca(from part 1)- Complete the game.
Lv.50 Class:Blademaster HP:1050 SP:160
Helba(yes, the hacker)- Read E-mail after talking to Aura at the end of the game.
Lv.99 Class:Wavemaster HP:9999 SP:999
Tsukasa(from .hack/SIGN anime)-Read mail after talking to Aura at the end of the game.
Lv.5 Class:Wavemaster HP:115 SP:40
Subaru(from .hack/SIGN anime)-Read mail after talking to Aura at the end of the game.
Lv.15 Class:Heavy Axe HP:425 SP:55
Sora(from .hack/SIGN anime)-Read mail after talking to Aura at the end of the game.
Lv.90 Class:Twin Blade HP:1665 SP:280
Mia(I thought she was dead...)-Complete the dungeon of Omega:Hidden Darkside Holy Ground.
Lv.45 Class:Blademaster HP:950 SP:145
How to beat Tarvos
You face Tarvos the third time you must travel through the dungeon of Omega: Cruel Vindictive Scars. Since you must take BlackRose, it would be stupid to take another swordsman (BUT I WANBA TAKE BALMUNG!!!), you should take a magic user like Wiseman(Since Elk is still P.O.d that you killed Mia). Or a better choice is Mistral, since she hasn't been around to level up in a while. Either way, all 3 party members should be of level 85 and up (once again, I was on a much higher level, but I have nothing to do but play games all day). Tarvos, like nearly every other Boss starts at 0 HP, meaning he cannot be damaged until after you cast Data Drain. Tarvos does all the normal spells and he can paralyze a Party Member, meaning certain death if you don't heal. Fighting Tarvos is similer to fighting Cubia. He starts with a Physical Tolerance and toggles between Physical and Magic Tolerance at random intervals. This is why you'd have to be a poor strategist to bring 2 sword users. Then you'd only have Kite to use Magic during its Physical tolerance. With Wiseman or Mistral, your party is balanced. Back to the fight, Tarvos, like Mia, has 3 "Super Spells". These spleels are: Data Drain, which is identical to the one Mia uses. Mallice Light, an area Spell causing 800 to 1200 damage(Yowie!!!). His most painful spell is the Cused Death Play. A single character is drawn into Tarvos, who skewers the character, killing him or her instantly. Ressurect fast or be wiped out as Tarvos can cycle between spells remarkably fast. After you manage to Drain him, he has a low 7000 HP and no tolerance. He can't cast Data Drain or Death Play, but he can still cast Mallice Light and his normal spells. Easier than Mia? Yes, but not by much.