The Last Story/Bandits' Warehouse

Let's split up and look for clues
When you enter the warehouse, seek out the guard's location. Your first job is to sneak up and take him out. Climb across the beam until you're behind the guard, then drop down and attack. If you drop down behind the boxes stacked up behind him, you can hide behind them and use Slash, which should take the guard out in one hit. When he's down, your allies will enter the warehouse and begin searching for the medicine. Look in the treasure chests: one in the back-right corner; another to the left of it (you'll need to squeeze through the gap in the stacks of crates); and another near where Lowell is, in the left of the room. When you've opened all three, Lowell will find a switch for a secret entrance. Walk up to it, and Dagran will ask you to look at the large snake-and-skull emblem on the wall. After the short cutscene, head down the secret passageway.

In a room down here, a group of bandits, including Zoran, their leader, are plotting an attack on the city. You're going to put a stop to that. Wait for Dagran's signal. On the count of three, run in and begin the battle. There are six bandits, including Zoran, though you only need to take out the five underlings. After the battle, Zoran pretends to flee, but instead hits a hidden switch, opening two trapdoors, causing you and your party to fall into the sewers underneath.

The sewer
You're now separated from Dagran and Lowell, leaving Mirania as your only ally. Swim out of the water to the left. When you reach land, some Reptids will join you. Defeat them, making sure to keep them away from Mirania, so she can use her healing magic. If your HP is low, keep the fight near Mirania's healing circles. After, look near the top-right of the back wall to find a drainage channel, which you can use to escape the room. Climb up the wall to reach it. Through here, follow the sewer to an apparent dead-end, where some Reptids will break through the wall and attack. Defeat them, then go through the hole they created, and turn right, to reunite with Dagran and Lowell. Dagran will point out a Reptid Gladiator, and will lure it down toward you. When it's near, use Slash on it. One hit should be enough. Head through the hole in the wall behind it. Through here is a Summon Circle, if you want to use it. Zael, at least, should be no lower than level 11 before continuing. This is to ensure you learn Gale, which allows you to diffuse magic circles (hold, then aim at a magic circle and press again). This causes additional effects for allies' magic, or nullifies enemies' magic; for example, diffusing Mirania's magic sends a burst of healing magic instantaneously to the entire party. When you're ready, climb up the ladder in front.

Up here, the cells are full of Reptids, though you can't do anything about them now. Save at the save point, then enter the door. The room contains several Reptids. Plan your attack, then wipe them out. It's best to start with the Reptid Healer, by diffusing its healing circle, then killing it. When they're dealt with, head through the door to the next room. Time for your first battle with an Ogre, a gigantic beast capable of high-power attacks at close range. Approach it enough to wake it up, then run out of its range, and seek out the pillar behind it. Have Lowell destroy it with magic. Chances are he'll be targeted exclusively by an archer, despite the effects of Gathering, requiring you to go up and take it out in order to give Lowell time to get a shot at the pillar. When the pillar goes, it'll take the ceiling, and hopefully the Ogre, with it. After that, it's a simple matter of picking off the remaining Reptids. Leave through the door to the right of where the Ogre was standing. Save through here before continuing.

Boss: Terracor
Inside, Zoran is waiting with a little surprise for you - a Terracor and a couple of Bandits. As Dagran says, you can use the landings to get a hit in on its vulnerable head. Hide behind the railings, then lure the Terracor over with Gathering, and use Slash when it's in range to send it rolling around the room. Eventually it'll get stuck in the door, allowing you to let loose on it. You can pretty much ignore the Bandits, unless they start getting in your way. When the Terracor gets free, repeat the process until it goes down. After the battle, climb up one of the ladders at the back of the room, and follow Zoran. After Mirania decks Zoran with a frying pan, and Lowell retrieves the medicine, you'll return to the tavern.