The gameplay is similar to previous entries in the Baldur's Gate series, with the player controlling a party of up to six characters, including the main protagonist, who can be custom designed at the beginning of the game. The player can also import their character from either Baldur's Gate or Baldur's Gate II: Shadows of Amn.
In expanding from the original game, Baldur's Gate II: Throne of Bhaal adds a number of features that distinguish it from the original:
It is set in a number of new locations in Tethyr.
It has a new level 40 experience limit, new high-level monsters, and new items.
It has a new dungeon, Watcher's Keep, which can be accessed from both the original Shadows of Amn game and the Throne of Bhaal campaign.
All of the non-player characters (NPCs) from the original game are available with the exception of Yoshimo. The game adds a new NPC, Sarevok, to the game.
The in-game plot is based on a war that breaks out in Tethyr amongst the Bhaalspawn. The player character (PC) must venture through regions including the city of Saradush, which is under siege by fire giants, a fortress in the Underdark, and a monastery in Amkethran. Through the game, the PC has to defeat five legendary Bhaalspawn, known as The Five. As the story progresses, The Five kill all their brethren, despite the efforts of Mellisan, a woman trying to save all the innocent Bhaalspawn and keep them safe in Saradush. Only when the PC kills off The Five and uncovers his own power is the truth revealed: Mellisan is in fact Amelyssan the Blackhearted, the mastermind behind both The Five and the slaughterer of all the Bhaalspawn. She was once Bhaal's high priestess, to whom he entrusted the task of his resurrection. She does not intend to resurrect the god, however. Instead, she is preparing to become the Goddess of Murder herself. With all quests finished and all Bhaalspawn killed, the PC must journey to the planar Throne of Bhaal for the great final battle against Amellysan. Ultimately, the PC is presented with the choice of either ascending the throne of Bhaal or destroying it and returning to peaceful life as a mortal. If the PC chooses to ascend, they have the option of either becoming the new God of Murder or becoming a deity dedicated to good and righteousness.
Melissan is a mysterious woman who meets the main character early in the game and offers help and information. Melissan claims to help the innocent Bhaalspawn who are caught up in the war and solicits the main character's help throughout the story. Her real motives remain mysterious throughout most of the game. Her true name is revealed to be Amelyssan the Blackhearted, and she is the mastermind behind the Five and the deaths of all Bhaalspawn. She is to become the new goddess of Murder and is the final enemy in the Baldur's Gate saga. She is voiced by Heidi Shannon.
Illasera is a weak elven Bhaalspawn with a lot of bravado. She is the first Bhaalspawn the PC encounters in the Throne of Bhaal. She is voiced by Grey DeLisle.
Yaga-Shura is a Fire Giant besieging the city of Saradush with his army. He would be invulnerable but for his Achilles' heel, his heart, whose destruction renders him vulnerable but no less fearsome. He is voiced by Kevin Michael Richardson.
Sendai is a drow cleric and mage. The PC does not get the chance to battle her immediately, but must first defeat wave after wave of statues of Sendai. She is voiced by Vanessa Marshall.
Abazigal is a half-dragon of great power. The PC has to first kill his son, Draconis, outside Abazigal's lair before setting up a meeting with him. Both Abazigal and Draconis begin fighting in human forms before changing into their immensely more powerful dragon forms during their respective encounters. Abazigal is voiced by Jim Cummings.
Balthazar is a good-aligned monk of immense power, who feels the only way to destroy the curse of Bhaal is to become the Lord of Murder and then end his own life. He is voiced by Jeff Osterhage.
Gromnir Il-Khan is a half-orc Bhaalspawn who is the leader of the town of Saradush. While at the beginning it is believed that he is mad and paranoid, his wild theories about Melissan turn out to be true. He is voiced by Jim Cummings.
Cespenar is an imp who can refer to his "secret recipes" in order to forge wonderful weapons from special bits of items that the PC collects along his journey. He claims that he is the main character's private butler and respects them as the "Great One". He is voiced by Jeff Bennett.
Solar is a celestial guide who resides inside a pocket plane dedicated to the PC. She is voiced by Charity James.
Demogorgon is a demon prince of tremendous power included in the Watcher's Keep expansion area as an optional boss. He is voiced by Jim Cummings.
Chris Chan of the New Straits Times gave a favorable review, concluding, "All in all, I enjoyed the epic feel of the game tremendously and loved the available customisation options."GameSpy awarded Throne of Bhaal its Best of 2001 PC Expansion Pack, and called the game a "brilliant end to a brilliant gaming saga".IGN awarded Throne of Bhaal an Editors' Choice Award. The Academy of Interactive Arts & Sciences named Baldur's Gate II: Throne of Bhaal as Role Playing Game of the Year for 2001.