The High Captains - NWN Main Quest (Chapter 2)
The High Captains is the second main quest of Chapter 2 and can begin one of 3 different ways. You can start this quest by speaking with either High Captain Baram or High Captain Luskan - you can find "images" of both these captains at the entrance to their lairs. Check my map screenshot below if you need help finding where either of these captains are located.
Alternatively, you can start this quest during the Strange Bedfellows Side Quest by speaking with Rhaine or Oreth in the Wink and Tickle Brothel. If you agree with Bela that both High Captains should be killed then she'll send you to speak with Rhaine or Oreth (depending on your character's sex) on the 2nd floor of the establishment.
Rhaine or Oreth will give you keys that will open the locked doors leading into Baram's Lair or Kurth's Lair. These keys are required to enter through the secret entrances for each of the High Captain's Lairs. Without these keys the only way you'll be able to enter is by smashing down the front door.
As aforementioned, when you enter either of the High Captain's areas you'll find an image (more accurately a projection) of them standing outside of the front gate. They will be friendly to you so long as you don't open the gate or step foot on their property through one of the secret entrances. Both of these High Captains will offer you a quest which will require you to kill the other captain and return their head.
You technically only have to kill 1 High Captain because all we need is a single seal to complete this quest and continue with The Search for the Cult... However, if you want to maximize the EXP earned I recommend you kill both High Captains and fully explore each area. Both areas have Side Quests that take place in them so they're worth exploring for more than just EXP from slaying enemies.
Also, once you defeat one High Captain you should turn in their head to the other one. This will allow you to claim the EXP and Gold reward before you make the remaining High Captain hostile. It doesn't matter which High Captain you eliminate first, they'll both give you the same reward for the other's head.
Those of you that did the Strange Bedfellows quest will have the keys needed to access both secret entrances; below is information about where you can find both of them.
Secret Entrance to Baram's Lair: You can find the secret entrance of Baram's Lair in the middle of the northern part of the map in the Sewers under Luskan. This location is a tad bit to the east of the Contraptulator machine that's used in Colmarr's Fantabulous Contraptulator.
Secret Entrance to Kurth's Lair: The secret entrance to Kurth's Lair is actually found just north of the normal entrance. You'll find a locked door in a half destroyed building that you can enter to reach the Harbor Sewers. The Harbor Sewers is a very short zone that will dump you out into the Harbor which is part of Kurth's Lair.
High Captain Baram boss fight
Inside the first part of High Captain Baram's Lair you'll need to kill the 2 Yuan-Ti Sorceresses that are standing around the ziggurat to proceed. At first both of them will be invulnerable to you but you can fix this by destroying the 2 "events" nearby. To the west of the ziggurat you'll find 2 gravestones that summon shadows - destroy both and you'll make the Yuan-Ti on the western side of the ziggurat vulnerable.
To the east of the ziggurat you'll find a bunch of skeletons praying to one central skeleton. Attack them and defeat them all to spawn a Greater Mummy - defeat that and you'll make the eastern Yuan-Ti vulnerable to attacks. In addition to these 2 Yuan-Ti you'll also want to search the nearby hallway to find the Nanny for the Nine Lives side quest.
Once you're past the 2 Yuan-Ti it's a straight shot to High Captain Baram. Make sure you remember to loot the High Captain's Seal from one of the chests behind Baram and Baram's Head from his corpse if you plan to give it to Kurth to complete his quest.
High Captain Kurth boss fight
High Captain Kurth's Lair is reached by traveling through the Luskan - Docks zone. If you take the secret entrance it'll put you in the Luskan - Docks next to The Ruins of Illusk dungeon. I recommend you do this side quest while you're in this area, it's one of 2 side quests that take place in Kurth's side of Luskan.
Inside Kurth's Lair you will find High Captain Kurth in the north central room. You'll find the High Captain's Seal that we need inside a chest in one of the side rooms connected to Kurth's room. Also, you'll find Evaine who is part of the Saving Evaine side quest in a side room as well.
The only other thing to mention in Kurth's Lair is the portal in the big room right before his. Here you will find a portal that endlessly summons enemies unless you close it. In order to close it you'll have to collect 2 items, a Smooth Token and a Glowing Sphere. Each of these items are found nearby, if you need help locating them use my map screenshot below.
Closing the portal is completely optional but it'll give you a little bit of EXP once closed.
Once both High Captains are dead this quest is complete. Alternatively, once you talk to Aarin Gend in the Temple of Tyr and give him a High Captain's Seal the quest will also be complete. You can continue progressing through Chapter 2 via The Search for the Cult quest.