Copper Coronet Overview - Baldur's Gate 2
The Copper Coronet is a bar in the Slums district of Athkatla and acts as the new 'Friendly Arm Inn' of Baldur's Gate 2. Inside of this bar on your first visit you'll find a couple of quests as well as the companions, Nalia, Anomen, Korgan and Hexxat. In the future most of the other companions that you dismiss from your party will come to the Copper Coronet after being dismissed to wait for you making this a base of operations of sort.
When you first arrive at the Copper Coronet it'll be run by a weird man named Lehtinan; ask him about "other sorts of entertainment" to gain access to the northern half of the bar where all the illegal stuff happens. In the northern most portion of this area you will meet a man named Hendak who will begin the side quest Free Hendak and the Slaves. During this side quest Hendak will take control of the Copper Coronet and he'll become the new proprietor. Nothing else significant will change though.
Aside from Hendak the most important people in here for you to talk to are Nalia, Firkraag, Hexxat and Joluv. Nalia will unlock De'Arnise Keep on your world map, Firkraag will give you a quest involving Windspear Hills and Hexxat will give you a quest involving the Graveyard District (plus unlock a new dungeon there). Last but not least Joluv is a vendor that sells some very powerful magical items.
Hexxat: Hexxat is one of the new companions added into the game for the Enhanced Edition. When you first recruit Hexxat to your party she'll be a Thief that asks you to travel to Dragomir's Tomb in the Graveyard District; when you complete the tomb you'll meet the real Hexxat. For more information about this quest as well as all the other tomb quests she asks you to do check out Hexxat's Companion Quest walkthrough.
Firkraag: His full name is Lord Jierdan Firkraag and this man is actually a red dragon in disguise. Speaking to him will begin the Journey to the Windspear Hills Side Quest and unlock this location on your World Map if it has not already been unlocked.
Nalia: Nalia is one of the potential companions in BG2 and when you speak with her inside of the Copper Coronet she'll begin The De'Arnise Keep Has Been Invaded Side Quest which will also unlock De'Arnise Keep on your World Map. It's strongly recommended you talk to Nalia to unlock this location and also complete this quest early on since it's rather easy.
Korgan: Korgan is one of the potential companions in BG2.
Joluv: This vendor was added into the game during the Enhanced Edition; previously he was only available to people who owned the Collector's Edition of the game. He sells a wide variety of extremely powerful items, check Joluv's wiki page for a complete list of all he sells.
Anomen: Anomen is one of the potential companions in BG2.
Llynis: Llynis is involved in the Put the Spirit of the Child Wellyn To Rest side quest after talking with Wellyn and accepting the quest you'll have to come and talk to Llynis in the Copper Coronet and either take the stuffed bear from him or kill him for it.
Hendak: Hendak is involved in the Free Hendak and the Slaves Side Quest and will become the future proprietor of the Copper Coronet if you let him out of his jail cell during this quest. In order to free Hendak you'll need the Beastmaster's Key which drops from the Beastmaster.
Beastmaster: The Beastmaster is involved in the Free Hendak and the Slaves Side Quest, he'll drop the key you need to unlock Hendak's cell.