Baldur's Gate 3 YouTuber SlimX has released a 25-minute video about all the offscreen tricks and shortcuts Larian used to make Baldur's Gate 3's first act work. Among them are a holding pen for plot-critical NPCs to hang out in, and a "magical teleporting death journal" to point you in the direction of Act 2 should you kill all the NPCs who would otherwise direct you there.
One consistently impressive thing about Baldur's Gate 3 is how elastic and responsive it is to player choice. Part of this comes from having more consistent rules than any RPG I've ever played. For example, items and characters never appear or disappear out of thin air. If you sell Dammon a +1 Dagger in Act 1, he'll still have it in his inventory come Act 3, because BG3 uses the same NPC data across the entire game rather than separate instances or copies like you might see elsewhere. To help support all of that, BG3 has some fairly unique and strange digital machinery whirring away behind the scenes.
A big focus of SlimX's video is something referred to in BG3's files as "the asylum." This is where characters who can't be found somewhere in the overworld get stored when they're not in use. Everyone from Mizora to goblin butler Sceleritas Fel hangs out in this digital green room when it's not their turn. Pantsless bard murder victim stand-in Quil Grootslag is also in attendance, as is "the Absolute," or at least an NPC stand-in who delivers the deity's voice lines from offscreen. There's even the full power, Act 3 boss fight-ready vampire lord Cazador, who's on-call for a dream cutscene experienced by player origin Astarion.
Halsin's Journal Vol. 2 is another curiosity you can find out here. It's meant to clue you in to the Shadow Curse and Moonrise, should you kill both Halsin and Minthara before they can tell you about them. The book will teleport into the inventory of whichever one of the two is the last to die, leading to its name in BG3's script files, "magical teleporting death journal."
There are plenty of other oddities out there as well. "The realm of naked men" makes an appearance, as do the backgrounds from character creation, level up, and some key cutscenes that don't have corresponding locations on the map. The version of the House of Hope seen in Act 1 is a small slice, separate from the real dungeon. There are also some early access and otherwise cut NPCs still hanging out, like Oscar-worthy Tiefling scammer Nerela.
One of the most surprising secrets, for my money, is a field of portrait backgrounds out in the void, the backdrops for our characters' little in-game icons. It's unclear to me how exactly they work, but I wonder if Larian's unique system for producing the portraits helps explain some of the persistent little bugs with the portraits, like the weird duplicates Oscar Fevras used to make.
More than anything, I find it gratifying to see what it took to get one of my favorite games running, and videos like this may prove useful to any Baldur's Gate 3 modders looking to make their own adventures with BG3's cracked toolkit. SlimX has also indicated that he might do a similar treatment for the game's other acts, and you can check out the YouTuber's full body of work over on his channel.
