Suikoden Shasarazade Barbarosa
Castle of Toran
After you finish Moravia and get Vincent at the top, go to the meeting room on the fourth floor. Agree to get ready for the Fortress of Shasarazade.
Watch the scenes as your army prepares for one of the biggest battles yet. Viktor gives McDohl the Steel Hatchet (Gremio's weapon).
The next day, go out to the port part of the castle. 500 boats have been made thanks to the Dragons, and your army is ready to attack Sonja Shulen's Floating Fortress of Shasarazade.
Battle at the Floating Fortress Shasarazade
The enemy has a whopping 17000 soldiers here. You should have slightly more if you have all 107 recruits at this point. Continue to use your Ninja's to figure out what the enemy will be doing. Sonja is capable of using magic or a charge on you.
Choose your party afterwards, Viktor must come with. Bring a powerful party, tough bosses are within. Go west down the stairs to get a Chaos Shield. Follow the path as you work south a bit then west once more for a Guard Ring. Southwest of here for a Master Garb.
Continue east, south, and then when you get to the T go west for a Mega Medicine. Rest up before you go south here.
Shell Venus is here. "There you are!" says Viktor. This Shell Venus has like 10000-12000 HP, so even though you can likely do a ton of damage at this point you will need to do it for several turns. Using Lightning Runes is nice as is Judgment by McDohl. I had Yam Koo and Tai Ho (level 16 weapons) using their unite to take off about 1500 each time it was used. 100,000 bits are your reward.
Take the Thunder Crystal, a high-level Lightning Rune. Very nice. Viktor shuts the sluice so run out, but as you leave it seems someone set fire early! Sonja Shulen rushes out, upset about the fire. She has about half the HP as the Shell Venus but your rune magic is probably expended at this point. Or at least a lot of it. Use your best attacks on her to put her away but her physical attack and magic can be devastating if you don't have the means of healing.
Outside the army is in flux, as Sanchez lit the fire early. Sanchez was the imperial spy (which is why he was never one of the 108 stars). Mathiu says not to execute him now so that morale does not plummet.
Castle of Toran
Back at the Castle, go to the basement to see a scene with Cleo and Sonja. Talk to Sonja and convince her to join, even if she hates you. Sonja is the last recruit, assuming you followed the guide up to this point. Save your game and then talk to Mathiu.
Mathiu wants to march on the capital. Once you talk to him he won't let you say no so hopefully you have all 108 characters at this point. And hopefully Pahn survived the Teo fight. If so, Leknaat will come and revive Gremio for the final fight.
The Last Army Battle
Yuber and Kanaan are waiting for you, with 100,000 enemies. But Lady Leknaat and Joshua combine their magic to magic 80,000 monsters disappear. Like the Shasarazade battle, you should have an easy time telling what the enemy will do with three ninja's and three thieve's on your side. If a thief fails just send out Joshua's dragon knights for some damage. Yuber Charge is dangerous so it would be great if your Ninja or Thief told you about that attack early on. With little effort you should be able to finish the last war battle. Hanzo from Rokkaku thanks you, even Zorak from the Warrior's Village is here.
Gregminster
Viktor and Flik join McDohl at Gregminster. Choose the other three characters. Hopefully an elite magician or two (Crowley, Luc, Hellion, etc) or a combo with a great unite attack (Tai Ho / Yam Koo, Sydonia / Varkas, etc).
At the bridge leading to the palace area, you see Ain Gide. He will not let you pass despite the Imperial Army being overthrown. He uses high level fire rune magic like Final Flame, so you will want to take him out quickly. Fortunately he has only 8000-9000 HP so 3 turns with your party should be enough, especially if McDohl can cast Judgment 3 times.
Gregminster Palace
As you enter, things look a little different. Take the Windspun Armor to the east (elite heavy armour). Now go northwest to exit, though you'll have to face some Imperial Guards along the way. Get used to them.
Head to where you met Barbarosa first, with your dad, but go behind this area now. Soon you will be fighting soldiers left and right, approximately 10 groups on one floor where you travel west a few steps, fight a group, and repeat. Make use of Hell, and use your magicians spells up. You will probably want to go all the way through here to kill off these mandatory soldier fights, then return to spend your bits on sharpening weapons and rest up.
When you get past that area, continue to go east in the next one until you reach a Horned Helmet. Northwest of here for a Power Ring and a save point. This is it, the end. Make sure you save here if you plan on transferring your data to a Suikoden II 2 play-through.
Emperor Barbarosa
Follow the path north until you reach the garden. Barbarosa does not plan on giving up of course. He uses his Dragon King Sword to turn into a three-headed Golden Hydra.
Fortunately, this beast only attacks once per round despite the three heads. It will either be an exploding-cocoon attack for good damage on one ally, or a thunder attack on the party for decent damage. Having a Flowing Rune user makes for each healing otherwise you'd have to bust out a Mega Medicine for everyone. This beast is strong against Lightning and you cannot use it at all on the middle head. The left-most head (it's RIGHT head in actuality) can heal the other heads, so defeat that one first. Then it doesn't matter which one you take out last. Because it only attacks once per turn you really should not have too much trouble.
No level up for defeat, as this is the end. Enjoy the ending and reading about the fate of the 108 Stars of Destiny for Suikoden I.