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1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsFor most players, take the Underdark first, then return to the surface and explore the Mountain Pass before entering Act 2. You can normally visit both areas in one playthrough, so this is not a permanent either/or choice.
For most players, take the Underdark first, then return to the surface and explore the Mountain Pass before entering Act 2. Baldur’s Gate 3 does not force you to permanently choose between these routes. You can normally visit both in one playthrough, and doing so gives you more quests, equipment, companion content, and story context.
If you truly want to choose only one, pick the Underdark for the broader collection of locations and stronger early-game preparation. Pick the Mountain Pass if Lae’zel, the githyanki, and the route to the Blood of Lathander are your priorities.
Mountain Pass vs. Underdark at a glance
| What matters to you | Best choice | Why |
|---|---|---|
| First playthrough | Underdark first, then Mountain Pass | You see the most Act 1 content without giving up Lae’zel’s storyline. |
| Completionist run | Both, usually Underdark first | The regions contain separate quests, encounters, locations, and rewards. |
| Lae’zel or githyanki story | Mountain Pass | Crèche Y’llek and its surrounding quests are central to this storyline. |
| Powerful early equipment | Underdark first | Grymforge, the Adamantine Forge, and other Underdark rewards can significantly improve a party. |
| Fastest route toward Act 2 | Mountain Pass | It provides the more direct approach to the Shadow-Cursed Lands. |
| Role-playing a githyanki or drow | Consider both | Both regions offer distinctive race-related interactions, while the Mountain Pass is especially important for githyanki identity. |
Why the Underdark is usually the better first stop
The Underdark is not just a short alternative corridor. It is a substantial Act 1 region with several connected areas, including the Myconid Colony, Decrepit Village, Selûnite Outpost, Arcane Tower, Sussur Tree area, Grymforge, and the Adamantine Forge.
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That density makes the Underdark particularly valuable before Act 2. You have more opportunities to gain experience, find alchemical ingredients, resolve side quests, meet factions, and collect equipment. The region also contains storylines involving the myconids, deep gnomes, and duergar, so skipping it means leaving a large portion of Act 1 unexplored rather than merely choosing a different road.
The Adamantine Forge is the biggest practical incentive
Grymforge leads to the Adamantine Forge, where you can craft up to two adamantine items. The game provides two pieces of Mithral Ore, so the forge does not offer unlimited crafting. Depending on your party, the available armor, shield, and weapon options can be among the most useful equipment upgrades available before Act 2.
The forge area also involves the Grym encounter and its associated quest content. It is worth planning around if you want to use the forge efficiently: decide which two items best suit your party before spending the ore, since you cannot treat the resource as an unlimited source of upgrades.
Other Underdark content worth considering
- Myconid Colony: faction quests, merchants, and story content connected to the colony and its visitors.
- Grymforge: duergar conflicts, deep-gnome content, the Adamantine Forge, and the Grym encounter.
- Arcane Tower: an exploration-heavy location with its own discoveries and rewards.
- Sussur Tree area: the starting point for the Sussur weapon branch.
- Selûnite Outpost and Decrepit Village: additional exploration, encounters, and routes through the region.
The Underdark is not automatically easy. It has numerous encounters, and the difficulty depends on your level, party composition, difficulty setting, builds, and tactics. Its advantage is breadth and preparation—not a guarantee that every fight will be less dangerous than what awaits in the Mountain Pass.
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The Mountain Pass and Rosymorn Monastery Trail offer content that the Underdark cannot replace. This is the main setting for Lae’zel’s githyanki storyline and leads to Crèche Y’llek, a githyanki base beneath Rosymorn Monastery.
Crèche Y’llek is a substantial story location, not merely a passage on the way to Act 2. It contains the zaith’isk, the Planecaster, Vlaakith-related story material, and quests involving Lae’zel, the artefact, and the githyanki prince. If you care about Lae’zel’s companion arc or want a clearer understanding of the githyanki conflict, the Mountain Pass is the route you should not skip.
The Blood of Lathander
The Mountain Pass also contains the quest for the Blood of Lathander, a legendary mace. Its value depends on your party and whether one of your characters benefits from that type of weapon, but it is one of the most memorable and valuable unique rewards available before Act 2.
The route has its own distinctive githyanki encounters and lore as well. Choosing the Mountain Pass is therefore not only a travel decision; it determines which major story material you see before moving into the Shadow-Cursed Lands.
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Best order for a normal playthrough
- Finish the Wilderness and Goblin Camp decisions you care about. Do not rush away while important quests, merchants, or unresolved situations still matter to you.
- Enter the Underdark. Explore the locations and faction content that fit your party and goals.
- Visit Grymforge. Complete the content you want there and use the Adamantine Forge if its items suit your builds.
- Return to the surface. Make sure you have dealt with any urgent surface quests before moving on.
- Enter the Mountain Pass. Explore Rosymorn Monastery, Crèche Y’llek, and the Blood of Lathander content.
- Make a manual save before the final transition into the Shadow-Cursed Lands.
- Enter Act 2 only after checking your unfinished Act 1 objectives.
This order is not required. You can start with the Mountain Pass and later return to the Underdark in the same run. The recommendation exists because the Mountain Pass naturally funnels many players toward Act 2, making it easier to overlook the Underdark if they treat the first route they enter as their only route.
Does entering the Mountain Pass lock you out of the Underdark?
Normally, no. The warning shown when entering the Mountain Pass can make the choice look permanently exclusive, but the two regions are generally both available during the same playthrough.
The more important risk is moving onward into the Shadow-Cursed Lands and, later, passing the major Act 2 story lock associated with the Shadowfell. Quest outcomes can also depend on your earlier choices and the current state of individual quests. Some situations are time-sensitive because of quest progression or area transitions, but it is inaccurate to claim that every Underdark quest has a fixed real-time timer.
The safest approach is simple: save before entering a warning-marked transition, complete urgent quests, and finish both the Underdark and Mountain Pass before committing to the late Act 2 progression. If the game specifically warns that something may change, treat that warning as meaningful rather than assuming every previous quest will remain untouched.
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Which route is easier?
Neither route is universally easier. The answer changes with your party level, class combinations, equipment, difficulty setting, and tactics.
The Underdark contains more encounters and can become demanding through attrition, especially if you explore widely without resting or improving your equipment. The Mountain Pass has fewer broad exploration opportunities but includes dangerous githyanki fights and concentrated story encounters. A party built to handle one type of challenge may find the other route more difficult.
If your concern is surviving Act 2 rather than minimizing immediate danger, the Underdark-first order is usually more useful because its extra experience and equipment—including the Adamantine Forge—give you more preparation before the Shadow-Cursed Lands.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What if you only want one route?
Choose the Underdark if:
- You are on your first playthrough and want the greatest amount of Act 1 content.
- You want stronger early equipment or plan to use the Adamantine Forge.
- You enjoy exploration, faction quests, and several smaller storylines.
- You are less invested in Lae’zel or githyanki lore.
Choose the Mountain Pass if:
- Lae’zel is a key member of your party or you want to follow her story closely.
- You are specifically interested in githyanki lore, Vlaakith, the artefact, or the githyanki prince.
- You want to pursue the Blood of Lathander.
- You want the more direct route toward the Shadow-Cursed Lands.
If you are playing for completion rather than speed, there is little reason to reduce the decision to one route. Do the Underdark, return to the surface, then do the Mountain Pass. The game’s warning is not a demand to abandon the other region.
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Should you use a guide?
You do not need a guide to make this choice or enjoy either route. However, readers who want a physical checklist for locations such as the Adamantine Forge, Crèche Y’llek, or the Blood of Lathander may prefer a Baldur’s Gate 3 strategy guide. It is an optional reference for tracking quests and rewards, not a requirement for playing successfully; a blind playthrough is often the best way to experience the game’s choices.
Final recommendation
Take the Underdark first, complete the parts that matter to your party, then visit the Mountain Pass before entering Act 2. This gives you the Underdark’s broader exploration and preparation rewards while preserving the Mountain Pass’s irreplaceable Lae’zel, githyanki, Crèche Y’llek, and Blood of Lathander content.
Only choose one if you have a specific reason: the Underdark for breadth and equipment, or the Mountain Pass for a faster Act 2 approach and the githyanki storyline.
Frequently Asked Questions
Can you do both the Mountain Pass and Underdark in BG3?
No. You can normally visit both regions during the same playthrough. The warning when entering the Mountain Pass does not usually make the Underdark permanently inaccessible.
Which should you do first: the Mountain Pass or Underdark?
The Underdark is usually better first because it offers more exploration, side quests, experience, and equipment, including the Adamantine Forge. Visit the Mountain Pass afterward for Lae’zel’s githyanki storyline and the Blood of Lathander.
Is the Mountain Pass easier than the Underdark?
The Mountain Pass is the more direct route toward the Shadow-Cursed Lands, but it is not universally easier. Difficulty depends on your party, level, builds, tactics, and difficulty setting.
The Bottom Line
Best overall route: Underdark first, Mountain Pass second, then the Shadow-Cursed Lands. If you must choose only one, take the Underdark for more content and early rewards, or the Mountain Pass for Lae’zel and githyanki story content.
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