Before you talk with Mathiu in the war room, you should make absolutely sure that you have recruited all 108 Stars of Destiny. This is your last chance to recruit anyone that you may have missed and receive the bonus and best ending; once you talk with Mathiu, this window closes. When you are prepared, proceed to the war room.
Talk with Mathiu and select to march to the capital, Gregminster. Leknaat will appear and tell you the story of her and Windy's Gate Rune. With the power of the 108 Stars gathered and the Gate Rune, Leeknaat will bring Gremio back to life and he will rejoin your party. This moment assures that you are on the path to the best ending. If Gremio was not brought back, either you have failed to recruit all of the Stars of Destiny or one of them may have been killed in battle. If you are going to convert your data over to Suikoden II, it is vital that Gremio be alive or you will be unable to achieve 100% completion in that game. With Gremio back, watch the scenes involving various members of your army and you will be back in the war room.
Tell Mathiu that you are ready to go to commence the final war battle of the game. While this is the climax of the war, it is still easily won with the ninja and thieves tactics. Make good use of the Dragon Knights and Strategists to increase damage as well. When you have won, watch the scenes as the party enters Gregminster.
A haunting wind blows as the party enters a mostly-barren Gregminster. Viktor and Flik will be required members of your party for the remainder of the game; which sucks, honestly. However, you can remedy this with a Gameshark, more on that in a little bit. For now, most of Gregminster is locked, with the exception of the shops (But not the inn).
Inside the shops is your last round of armor in the game. The Silver Hat, Master Robe, and Earth Shield, all of which are the best equipment in the game for some characters, and have been mentioned earlier, are now for sale here. Potch will go quickly, but in the upcoming areas, it is fairly easy to max out the amount of potch you can carry through battles. When you are ready, set off towards the Palace.
Ain Gide, whom you may recall meeting way back at the Kwaba Fortress early in the game, will oppose you entering the Palace. Extremely easy battle here. Throw everything you have at him. When the battle is over, Ain Gide will fall protecting Emperor Barbarosa, and your party will stand before the courtyard of Gregminster Palace; the final dungeon in the game. Before we finish this, there are some new things outside of Gregminster to take a look at. The next part will be how to remove Viktor and Flik from your party using a Gameshark. If you aren't interested, please skip by the next couple of portions.
The first thing you should do is take the Blinking Mirror back to your castle while having your party full of six members and then save. Punch in the code located above, with whatever version of Gameshark you may be using, and then load your previous saved game.
Go into your formation screen and select your sixth character. In my case, this is Rubi. Move that character into Viktor and Flik's place in the formation. Nothing will appear to happen, but exit the menu entirely and go back in...
You will find that character has overwritten Viktor and Flik and become duplicates of his/her self. Although this looks bad, don't worry, go ahead and save your game and then restart your game with the Gameshark off.
Upon loading your game, simply visit Sanchez or Mathiu and remove the duplicated characters from your party. You will also see that Flik and Viktor have been moved to the available characters to add to your party. Just a warning, if you add either of them back, they will become locked in your party again and you will have to duplicate this code again. You are now safe to use any party you wish for the remainder of the game. One thing I should note though: While you can fight the final boss with whatever party you choose, shortly after the ending starts, the game will freeze without Viktor and Flik in your party. So, in order to view the entirety of the ending, you will need them both in your party. With that out of the way, let's look at what is going on outside of Gregminster now.
All of the old enemies around Gregminster have been replaced by new, much tougher ones, and they each have rare items to drop. First, the Ninja Master, will drop the Crimson Cape accessory. You should have one of these already, but it is the best def-based accessory in the game behind the kobold-only Gold Necklace. Ninja Masters are your only source for more of these and do not underestimate them either; they are generally much faster than most characters and can hit hard.
The bird-like Simurgh enemy house Thunder Runes. You got one back in Shasarazade, but the Simurgh is your only choice to get more to outfit your mages.
And finally, the last antique in the game: The Beauties of Nature painting. You can rarely find these by defeating Orcs. If you've been getting all of the rare drops up until this point, you should now have every antique in the game.
For completionists, you are also going to want to revisit the towns Rockland, Lenankamp, and Sarady, as well as the dungeons Mt. Seifu and Mt. Tigerwolf (Which Sarady is beyond, if you forgot). Doing so will add them to Viki's list of teleport destinations. If you will recall, the two mountains are home to enemies that drop the Water and Earth (Wind) Rune Pieces which are the only rune pieces you can acquire as many of as you would like. Nothing else is new in these towns, except you can view a few optional scenes there with specific characters.
If you take Krin to visit the guy on the second floor of the inn in Lenankamp (Krin robbed this guy earlier in the game), you will see a short scene and Krin will run back to your castle; actually being ejected from your party as well.
Also in Lenankamp, you can take Meg to visit her parents here for a nice scene.
Finally, with Clive in your party, search the upper-left tombstone in Rockland for a bit of backstory. This will be played out in Suikoden II (Assuming you are prepared to hustle and beat the clock...). Before we move on to the finale, I just want to take a moment to list out the various castle collectable items and their locations. You should have them all already, but if not...
- Window Setting 0: Inside a chest at the Secret Factory.
- Window Setting 1: Inside a chest at Scarleticia Castle.
- Window Setting 2: Inside a chest in the Dragon Knights' Fortress.
- Window Setting 3: Dropped by the Sunshine King enemy in the Dragon's Den.
- Sound Setting 0: Inside a chest at Soniere Prison.
- Sound Setting 1: Inside a chest in Neclord's Castle.
- Sound Setting 2: Inside a chest in Seek Valley.
- Sound Setting 3: Dropped by the Siren enemy at Shasarazade.
- Old Book Vol. 1: Inside a chest at Pannu Yakuta.
- Old Book Vol. 2: Inside a chest in the Cave of the Past.
- Old Book Vol. 3: Search the bookshelf in Qlon Temple.
- Old Book Vol. 4: Search the bookshelf on second floor of the Dragon Knights' Fortress.
- Old Book Vol. 5: Inside a chest in the Dragon's Den.
- Old Book Vol. 6: Inside a chest in Soniere Prison.
- Old Book Vol. 7: Inside a chest at the Northern Checkpoint.
- Old Book Vol. 8: Inside a chest at the ruined town of Kalekka.
That's it; there's nothing left to do in the world of Suikoden but to enter Gregminster Palace and confront Barbarosa.
