Luskan

Finally you're done with this wretched Port Llast and you won't be seeing it ever again. Luskan isn't a pretty place to be either but we must press on. In Luskan you emediately find yourself in combat but your main priority now is to get to the temple. It's in the middle of the map (maybe slightly to the west). Once you get to the temple, Aarin will give you a quest to get inside the Host Tower and search for any clues and so on.

Entering the tower:

You have two or maybe even three choices how to get inside the tower. You can go to high-captain Baram (northeast) and accept his quest or go to Kurth (southwest). Or you can do as what I did. Kill them both and have lots and lots of cool items.

High-captain Kurth: He is the muscles and no brain type of character. Dealing with him requires either a lot of magic (which works very well) or having a tough melee character that could knock Kurth down. Anyway, getting around the docks can be frustrating as almost everyone is armed with ranged weapons so having a high AC and some sort of protection from piercing damage is a good idea. Once you get to the big door (the entrance to Kurth's "castle") you will be attacked by a big ogre brute. He has a lot of hit points and is capable of doing lots of damage but falls easily to mass damage spells and any fighter can end his reign of terror in an instant. Once you enter Kurth's "castle" you can either go straight and try to save the books that nasty goblins are burning or go straight to Kurth and kill him. The books that those goblins are burning contain various spells and tokens that I've found useful.

I haven't done this before but you might find it interesting: there is Burke's corpse somewhere in a small central room and it contains a journal and a token. Then go to a room to the northeast and search the fountain for another item. Then go to the west portal room and put both the token and the sphere into the portal to close it. This should make the battle with Kurth easier but I haven't tried this trick.

And to the very north lies Kurth - the weakling. He is not that weak but he doesn't like spells very much so if you happen to be a mage or a sorcerer you will fight this battle easy and fun. If you are a fighter type then knockdown can work wonders. After defeating him search the nearby rooms for some nice items and the High-captain Seal. You can also free a prisoner and get a reward later.

High-captain Baram: This rat lies in the sewers as it should. You will find that his lackeys aren't really human and have been infected with lycanthropy. In the "rat" form, they have immunity to +1 weapons if I'm not mistaken. I think they get a bonus to damage immunity and an AC bonus too. You may succeed to kill them while they're in human form sometimes. The necromancers in the summoning room will be invincible unless you take proper actions. At both ends of the room there are doors that lead to a specific "power-those-necros" room. Destroy everything and everyone in those rooms to take off the invincibility of the necromancer Yuan-tis. Once you've dealt with the necromancers, take the key on one of the bodies and go forth.

Once you reach Baram you will find that he's in a "rat" state but that won't help him much. He has support too. The supporters do more damage to you so be sure to take them out (and the statues). The rat falls easier than Kurth in my opinion so you should have no problems. After dealing with him search the chests for some magical items and High-captain's Seal.

After dealing with both or one of the captains and retrieving the Seal, go back to Aarin and you will have a fully functional pass to the tower.

Other quests: Most of secondary quests are too easy and are not worth attention but on or two are worth considering.

The Fantabulous machine: In the Magical Trinkets shop (I think) speak with Colmorr and you can ask him about his invention and eventually you get a quest to fix it. Now you must find four levers of the machine.
Lever one: Winkle and Tickle (or whatever) tavern/inn/building there's a room with a guard dog in it. The first lever is there.
Lever two: southeast sewers. Enter through the middle hatch.
Lever three: southwest sewers. You first need to spare the ghoul and accept his quest and complete it. He will give you the lever as a reward.
Lever four: I was surprised that the fourth lever was already inserted into the machine. Northwest.

There's an interesting quest in Kurth's area. There's a statue somewhere in the area and an abandoned house.
First seal: in the abandoned house kill the skeleton and take its head and put it on the altar.
Second seal: kill the fallen hero, take his heart and place it on an altar.
Third seal: kill the water elemental and place the blessed water on the altar.
Fourth seal: you'll have to fight Voleron the Damned! He is extremely tough and can kill you in a few hits. Stay away from him and do anything you can just don't get close to him. After defeating him, reap the rewards.