One of Baldur's Gate 3's earliest fully custom quest mods has you search for the nose of a clown living in a weird circus dimension, because of course it does
With help from a freshly modified version of Larian's toolkit, you can head through a portal and have chat with a strange man in a tent.
Not long after Larian released its official modding toolkit for Baldur's Gate 3, it took next to no time for modders to find out how to unlock extra functions that've helped get the ball rolling on the likes of custom maps and possibly full custom campaigns further down the line. Using a modified version of those official tools, one modder's now put together what looks to be one of the game's first fully-custom quests.
To my knowledge this isn't the first attempt at adding a quest to BG3, with Family Legacy being a pre-modding example that accomplishes its goal using notes and some unique items, but it does appear to be one of - if not the first - to make use of both the custom location creation and in-depth tweaking of NPCs/quest mechanics that these new tools can make possible.
The goal of this mod, Soul of Kiran's 'Clown Tent MoonGlasses Showcase', is to show off what's possible with 'Moonglasses - BG3 Extended Toolkit'. This is a project produced by a number of BG3 modders on Discord that aims to build on the stuff made possible by modder Siegfre's 'BG3 Toolkit Unlocked', by facilitating things like more advanced dialogue and cinematic tweaking.
As you can see in the video below, the clown tent showcase is basically a very short custom quest added to the start of Act 1, that sees you take a portal into a weird tent dimesion where a clown named Agnesius - voiced by the modder themselves - chilling, pink hair and all.
During a chat with him, you'll either end up agreeing to retrieve the nose that funnyman lost during "the great clown war" - cue my brain filling with shots of that Willem Dafoe scene from Platoon, but with someone called Juggles - or informing him that you aren't a fan of clowns.
If you retrieve the nose, which even squeaks if you move it around in your inventory, you'll do so via a custom quest listing that should lead you to finding it near the Nautiloid crash site, and bringing it back to complete your mission.
On the other hand, if you anger the clown during that first combo, you can initiate combat and slaughter him, leaving the nose lost to the ages. You can also pick the nose up before you even meet him for the first time, with this being programmed as an alternate way for the quest to trigger and direct you to the tent.
All in all, this little mission shows off "custom map levels, dialogues [made] from scratch, dynamic timelines & cinematic cameras, custom voice-over, custom journal quests, [and] advanced dialog logic & triggers". So, hopefully it's just a taste of what modders might be able to accomplish custom campaign-wise further down the line.
Some other BG3 modders have recently been busy adding real-time combat and custom romance cutscenes to the game, which are also well worth checking out, even if the former is still very much in an experimental stage.