Main Quest
The 18 story beats of the Mandate of Heaven, in order. Each links to the stage that covers it in detail.
New Sorpigal Stage 1
Before the plot proper begins, set your party up. Gather the opening quests in New Sorpigal, then exploit the rooftop teleporter to the Shrine of the Gods (a Dragonsand island) for a permanent +20 to every stat on all four characters, and loot the adjoining New World Computing dungeon for repeatable gold and endless food. This is the springboard for everything that follows.
Free Haven Stage 2
The spine of the game is the High Council of Free Haven: to win their approval you must complete one quest for each of the six Lords (plus an extra for Regent Humphrey in Castle Ironfist — seven quests in all). Begin collecting them now, starting with Lord Newton in Mist and Lord Temper in Castle Temper, and pick up the promotion quest for each of your classes from the same town lords. These quests stay open in your journal and are cleared across the next several stages.
Castle Ironfist Stage 2
The first and easiest promotion. Visit the inn at Rockham, where Chadwick Blackpoole nominates your party, then report to Lord Osric Temper in Castle Temper to become a Cavalier. While there, take Temper's council quest (clear the Devil Outpost) and his Champion promotion quest for later.
Bootleg Bay Stage 6
Sail or walk to Bootleg Bay and drink from the Fountain of Magic, then return to Lord Newton in Mist to be promoted to Wizard. This opens the higher elemental-magic tier and unlocks the path to Archmage.
Misty Islands Stage 7
Clear the Silver Helm Outpost in the Misty Islands and rescue Melody Silver, then return her to Regent Humphrey in Castle Ironfist to earn the Crusader promotion. Humphrey also hands you the Hero quest (slay a named dragon) for later.
Castle Ironfist Stage 7
Grind through Corlagon's Estate (the spectres hit brutally hard) to defeat Corlagon the Power Lich and claim the Crystal of Terrax. Bring it to Lord Newton in Mist for the Archmage promotion — the top of the magic ladder.
Free Haven Stage 10
In Free Haven, hire a Carpenter and Stonecutter and rebuild the ruined temple to become a Priest. Then fetch the Sacred Chalice from the Temple of the Sun (Bootleg Bay), place it in the rebuilt temple, and report to Lord Stone for the High Priest promotion.
Frozen Highlands Stage 10
Raid Icewind Keep in the Frozen Highlands for the Dragon Tower keys and report to Lord Stromgard to become a Battle Mage. Then use the keys to repair every Dragon Tower in the kingdom and return for the Warrior Mage promotion.
Mire of the Damned Stage 10
Descend into the Dragon's Lair in the Mire of the Damned and slay the named dragon Longfang Witherhide for the Dragon Claw. Take it back to Regent Humphrey in Castle Ironfist to be promoted to Hero.
Free Haven Stage 10
The druid ladder is timing-gated. Pray at the Circle of Stones on an equinox for Great Druid, then solve the altar puzzle in the Temple of the Moon (Free Haven) and pray there during a full moon, reporting to Loretta Fleise in Silver Cove for the Arch Druid promotion.
Silver Cove Stage 10
The hardest promotion fight. Storm the Warlord's Fortress in Silver Cove — packed with Death Knights — for the Discharge Papers, then return to Lord Temper in Castle Temper to become a Champion, completing the warrior ladder.
Free Haven Stage 12
Close out every Lord's council quest so the Free Haven council will hear you: Lord Kilburn's Shield (Blackshire) for Humphrey, the Devil Outpost (Demon Lair, Kreigspire) for Temper, the Hourglass of Time (Gharik's Forge) for Newton, the 9-stable price fix for Fleise, the Prince of Thieves (Free Haven Sewers) for Lord Stone, and ending the endless winter (the Kreigspire Hermit) for Stromgard.
Kriegspire Stage 12
With every Lord satisfied you head for the council — only to be turned away by Representative Silvertongue, who refuses you access to the Oracle. Humphrey sends you to the Superior Temple of Baa in Kreigspire; recover the Letter from Zenofex there as proof of his treason.
Free Haven Stage 12
Show the Letter from Zenofex to Humphrey; the council expels Silvertongue and your reputation jumps to SAINTLY. Now granted access, you descend to meet the Oracle, which gives you the final chain: retrieve the four Memory Crystals and the Control Cube.
Free Haven Stage 13
Gather all four crystals and seat each in the Oracle's chamber corridors: Alpha from the Supreme Temple of Baa (Hermit's Isle), Beta from Castle Alamos (Eel Infested Waters), Delta from Castle Darkmoor (Mire), and Epsilon from Castle Kreigspire. Each placement is worth a large experience bonus.
Dragonsand Stage 14
Brave the Tomb of Varn in Dragonsand — the hardest dungeon in the game. Collect the six code scrolls and Crystal Skulls, survive the radiation rooms by entering the reversed passwords in the pools, and open the Varn chest to claim the Control Cube. Return it to the Oracle.
Castle Ironfist Stage 15
The Oracle opens the Control Center. First find the Third Eye (a well west of Castle Ironfist) to get Nicolai's bell, ring it in the Ironfist library so Archibald frees himself, and collect the Ritual of the Void scroll — keep this scroll for the good ending. Then enter the Control Center to learn the alien Blaster skill and pick up Blaster Rifles, the only weapons that can destroy the Hive's reactor.
Sweet Water Stage 15
Storm The Hive above Sweet Water. Use the safe pads against the Flush, take the Hive Sanctum Key, and destroy the alien Reactor with your Blasters. Kill the Demon Queen, then exit through the back of the Hive — making sure you carry the Ritual of the Void scroll — to win the game.
Carry the Ritual of the Void scroll out of the Hive. When you exit The Hive's back door with the Ritual of the Void scroll, the alien reactor's explosion is contained by a great globe over Sweet Water instead of consuming the world. Your party is feted in Castle Ironfist and knighted by Prince Nicolai for saving the Kingdom — with a final wink that the figure thanking you is really Archibald (“thank you for saving my Kingdom”). If you leave without the scroll, the reactor's chain reaction destroys the entire planet — the Oracle warned you to escape with the Ritual of the Void. (Note: the GameFAQs guide idiosyncratically labels the world-destroying exit its “better ending”; the canonical kingdom-saved victory is the one taken with the scroll, as the in-game scroll and the Oracle both make clear.)