Players begin the game by creating an adventuring party of up to six characters, either by creating new characters or importing those from a previous game. Each new character created requires the player to provide them with their name, gender, race, class, and alignment, and then determine their ability scores and weapon proficiencies. The class of a character affects what alignments are available to them, what weapons and combat styles they can use, and how proficient they can be in them. Characters designated as thieves require the player to allocate points to the various thieving skills, and spellcasters need a few 1st level spells selected for their spellbook and then one memorised for use at the start of the game. Once a party is created, characters earn experience points in the game through completing quests and defeating enemies, and level up upon earning enough. Leveling up will automatically increase a character's hit points, grants spellcasters access to more spell slots including higher levels of magic, sometimes allows additional weapon proficiencies, and allows thieves to improve their thieving abilities.
Plot
In the town of Easthaven a party of adventurers resting in its tavern are met by the town's leader, Hrothgar (voiced by Jim Cummings), who invites them to join him on an expedition to investigate the town of Kuldahar, after a messenger sent from there reported of strange happenings. On the road to Kuldahar, the expedition is ambushed by frost giants, who cause an avalanche, blocking the path back to Easthaven. With only the adventurers surviving, they continue to Kuldahar and meet with Arundel (Jim Cummings), the village's archdruid, who explains that a mysterious evil force has been kidnapping villagers, and causing abnormal weather patterns and monster behaviour, resulting in the magical warmth provided by the giant tree that the village resides under to begin to recede.
Asking for their help to discover the source of the evil before the tree dies, the adventurers begin by searching the Vale of Shadows, an area containing Kuldahar's crypts, due to rumours of undead creature sightings, but discover from a cursed barbarian spirit named Kresselack (Tony Jay) that the threat lies elsewhere. Reporting this back to the druid, Arundel instructs the group to retrieve an ancient scrying item called the Heartstone Gem, so he may discover the source of the evil more quickly. After finding that the gem was stolen from a temple that the druid suspected it to be in, the party travel to the caverns of Dragon's Eye, finding a number of the missing villagers being held there by lizard men, and eventually finding the gem being used by powerful demonic creature named Yxunomei (Tara Strong). After killing Yxunomei and retrieving the gem, the party return to find Kuldahar under attack, and that a shapeshifter disguised as Arundel had attacked the archdruid. After the shapeshifter vanishes, the group find the real Arundel, who advises the party to take the Heartstone to Larrel (Michael Bell) at the fortress of the Severed Hand, the only one capable of using it now, before dying from his wounds.
Arriving at the fortress, the party discover that Larrel had gone insane, and aid him with a task he mentions, helping him to regain his sanity. Using the gem, Larrel discovers the source of the evil to reside in the former dwarven city of Dorn's Deep. Fighting their way through the city, the group eventually come across the source of the evil in the form of a priest who came to the region – Brother Poquelin (John Kassir). Poquelin reveals himself to be a demon who was exiled from his home realm by his superiors, and that both he and Yxunomei maintained a vendetta against each other that was getting out of control. Predicting she would follow him to the material plane, the demon sought a base of operation in the region to form a military force that could crush her, and while doing so, stumbled upon the ancient artifact Crenshinibon, which he claims had been "calling" to him. Poquelin immediately used its power to help him amass an army that he planned to use in conquering the lands of Icewind Dale, until Yxunomei's activities around Kuldahar led to the formation of Hrothgar's expedition. Seeking to stop it, the demon had his frost giant minions crush the expedition, but did not count on the adventurers' survival being a problem until they recovered the Heartstone Gem, forcing him to eliminate Arundel. Despite the party having found someone else to use it, Poquelin had managed to build up his forces, which he soon sent to Easthaven.
After fighting with him, the party finds itself transported back to Easthaven, which is now in ruins. After freeing the surviving villagers, the local cleric of Tempus, Everard, informs the party that Poquelin is going after Jerrod's Stone, a mystical object housed under the town's temple, which acts as a seal on a portal to the Nine Hells of Baator that was opened during a major battle between the combined might of the barbarian tribes and an army of a powerful mage, and which was sealed shut by the sacrifice of the shaman Jerrod who led the barbarians in the conflict. Gaining entry into the demon's crystal tower that enveloped the temple, the group discover that Poquelin's true intention was to reopen the portal contained within the Stone, allowing him to conquer the North with an army of demons at his command. Although he successfully achieves this, Everard, having shunned the tale of Jerrod's sacrifice until finally understanding what he did, throws himself into the portal and seals it off at the cost of his life. The party use the time he buys them to fight Poquelin in his true form as the devil Belhifet, and manage to defeat him, banishing him to the Nine Hells and escaping the tower as it collapses. In time, Easthaven eventually recovers, and the town is reconstructed.
In a twist ending, it quickly transpires that the game's narrator (David Ogden Stiers), was really Belhifet, who spent a mandatory century of imprisonment at the hands of the adventurers that is now close to end, and that he will soon walk the Prime Material once more to seek his revenge. (see Baldur's Gate: Siege of Dragonspear)
