Return to the Mercenary Fortress with Tsai in tow. Viktor will attempt to send you to Muse before the battle begins, but you have the option to stay and fight with them. You can choose to leave, but you will eventually be forced to have to come back and fight. Flik will challenge Riou to a duel to see if he has what it takes to battle beside them. Duels in Suikoden II are the same as they were back in the original game; like rock-paper-scissors. You try to guess by the opponent's words what their next attack will be. Attack beats Defense, Defense beats Wild Attack, and Wild Attack beats Attack. This duel itself, is only difficult if you haven't sharpened Riou's weapons at all or have poor armor equipped. In the end, Riou will successfully wound Flik and he will agree to let Riou lead a company.
That night, Jowy will suggest that we name our company. This is important because the name you choose here will become the name of your army throughout the entire game. While there is no official name, the Dunan Army is considered to be what it is known as, but pick whatever you like. In the morning, Pohl will wake you up informing you that the Highland Army is approaching. This is your last chance to use the warehouse for a rather long period of time, so make absolutely sure you store anything you won't be needing for a while. When you are ready, go outside to the courtyard and the battle with commence.
Army battles in Suikoden II are a lot different and more fun than its predecessor's. These next two battles are mainly story-driven and just a tutorial. Viktor, Flik, and Tsai will be controlled by the computer and attack with the Fire Spears. Riou can do the same or you can just hang back. The battle is over after a couple of turns. Shortly afterwards, you will be thrown into a second battle. In this one, simply stay put and wait until one of the Highland soldiers enters the Fort and the battle will end.
The scene will switch back to Riou and Jowy inside the Fort and you should select to accompany Jowy to find Pilika. You can fight various battles around the Fort with Highland soldiers if you like, but your destination is the war room. Inside the war room, Luca kills Pohl and turns his sword on Pilika, but Riou (If you selected quickly enough to save her) and Jowy will block Luca's sword. Luca easily throws them both off him and goes for Pilika again; thankfully, an explosion is heard and Viktor and Flik rush in for the save. The party flees for Muse City as the Mercenary Fort burns down. Outside, Riou, Jowy, and Nanami are joined by three random party members that you recruited thus far (Tsai being an exception). Return to Toto Village on your way to Muse. Inside, follow Pilika as she leads you to the shrine cave in the back.
Watch the scenes inside and Riou and Jowy will be met by Leknaat. She will advise them to take up the power of the runes that lay further within. Riou will receive the Bright Shield rune while Jowy will obtain the Black Sword rune; both True Runes. When you return to your party members, check out your new runes, and cross the bridge over to Muse.
Muse appears to be on lockdown when the party arrives. Nanami will try her best to get inside, but it looks like we aren't getting in without a permit. Riou and Jowy will drag a fuming Nanami away from the entrance to try to figure out how we can get our hands on one. Our next stop is the White Deer Inn which is directly east of Muse City.
You'll meet Hilda at the White Deer Inn, followed by her eccentric husband, Alex. Watch the scenes to find out that Alex just happens to have a permit to get into Muse. However, he's not going to let us use it unless we go treasure hunting with him first. There is a small item store and a rune master sitting at the tables here that you can make use of. If you need to sharpen weapons, you can head back out to the world map and south to Coronet. When you are ready, enter the Sindar Ruins that are located at the very back of the inn.
The Sindar Ruins is going to be the largest dungeon you've met thus far. Your goal here is to find the various Plates scattered around and set them in their indentations, unlocking doors. Make sure you navigate the twists and turns and pick up the chests along the way. Look for an area where it is clearly pointed out to you that you need to push a statue upon a switch; this will lead you to a pedestal with the Round Plate on it. This Plate is used to the north, going back the way you came.
The Triangle Plate lies to the west, across the bridge, of the area that contains a four-way fork. Take the Triangle Plate to the north-eastern path to find the sluice gate. Placing the Plate inside will drain all of the water from the area, allowing you to navigate the Ruins' canals. Closing the sluice gate also brings some new monster encounters to the area.
Once the sluice gate is closed, you will begin to encounter the Salamader enemy. This monster will drop the extremely rare, and missable, Fire Lizard Rune. There is one of these in a chest in the dungeon, but if you want more than one, this is your only chance in the game to do so. Once the boss of this area is defeated, all encounters here will cease for the remainder of the game and thus you will no longer be able to obtain this rune again. The rune itself, while powerful early on, isn't that great. It is attached to a weapon and works similar to Zamza's Fire Dragon Rune. On every normal attack you make, you will cause a good deal of fire damage to the enemy, but will also suffer fire damage, yourself, and if you're not careful; killing yourself. Later in the game, once you have a Rage Rune, this does pretty much the same thing but without the drawback of you suffering damage from the attack. You can negate this with a Fire Sealing Rune (Which most people give Zamza anyway) so it could be an option for him, if you'd like something different.
To find the Square Plate, go back the way you came, and the north into the drained canals of the Ruins. Go south to the next screen, then take the next west path to find the Plate. There are actually two Square Plate indentations and you need to do some backtracking to one of them.
Take the Square Plate back to the fork where you went west to get the Triangle Plate, but instead, go east and you will find a place for the Square Plate. Inside are chests with a Magic Drain Rune and the Old Book Vol. 2. In my opinion, the Magic Drain Rune is the absolute best rune to place on Riou's weapon. When you attack, it has a chance to restore the character's lvl 1 spell by 1MP. On Riou, it will allow you to consistently cast Great Blessing on the party throughout a long dungeon, without the need to leave and rest. This can also be useful for a bearer of a Water Rune and Kindness Drops. This is the only Magic Drain Rune you can freely add to a character in the game, so choose its bearer wisely. For the last Square Plate door, head to the west of the area where you entered the canals and you will find a save point and the door.
What'd you expect with the two-headed snake statues seen around the Ruins? Now that you have the Bright Shield Rune and can heal multiple allies, this boss is nothing to worry about. He's weak against fire, so if you happen to have a Fire Rune bearer, the better. If not, basic attacks and unite Riou and Nanami while using Jowy's Black Sword Rune.
The Double Head drops the very valuable Spark Rune. This is the only one you will find in the game. When attached, the entire party's SPD stat becomes the equivalent of the bearer; assuming that it is higher than the other characters. Thus they will act quicker in battle and have a much higher chance to strike multiple enemies in one attack than a slower character normally would. Excellent for Nanami. After the battle, continue up to the treasure chest and watch the scenes as the party leaves the Ruins and returns to the White Deer Inn. Like I stated earlier, with the Double Head defeated, there will be no more random encounters in this dungeon, so you will be unable to get another Fire Lizard Rune.
When you return to the Inn, the party will find Hilda collapsed inside. The party will panic as to what to do, but have Riou return to the entrance of the Sindar Ruins and pick up the Healing Herb that Alex kicked away in disgust. Bring it to Nanami and it will save Hilda's life. In thanks, Alex will hand over his Entry Permit and the party can now get into Muse, hopefully...