Players of Baldur's Gate 3 are discovering substitute Tieflings who replace anyone you kill in Act 1
Baldur's Gate 3 does not hold your hand, nor does it do much to prevent you from making terrible, dreadful, world-ending mistakes. Instead, as many be...

Baldur's Gate 3 does not hold your hand, nor does it do much to prevent you from making terrible, dreadful, world-ending mistakes. Instead, as many beleaguered game masters can appreciate, it finds various ways to take your decision-making into account. And as one player has discovered, this includes the creation of a whole array of characters that most players will never encounter, as they only appear in the game if you carry out some rather arbitrary killings early on.
The YouTuber Proxy Gate Tactician has taken it upon themselves to play through Act 1 in a manner that most players would not choose. Without delving into spoiler territory just yet (more on that later), this entails not only committing cruel acts of unnecessary murder but also requiring assistance to those one slaughters. This mixture of good and evil deeds is so nonsensical that most players would completely overlook it, yet Larian Studios has ensured that anyone who embarks on this path will have a unique Tiefling group at their camp, comprised of characters who would otherwise never be encountered.
As Proxy Gate Tactician has explained, the requirement for this is somewhat intricate. Once you gain access to the Druid Grove, you must kill all the Tieflings who would typically join your camp party later in Act 1. However, instead of slaughtering the entire grove, you should proceed to the Goblin Camp and eliminate all the leaders there, just as you would if you were to aid the Tieflings.
By doing this, the quest will be completed, and the Tieflings you did not murder will set off for Baldur's Gate. However, the characters who join your party have never been seen before, as they do not belong to the refugees wandering in the grove. With these entirely new characters, you can interact with them as you would with the typical party members, but they remain unique and do not simply adopt the dialogue options of their deceased counterparts. One of them will even request to dance with you—an experience not attainable with the regular group.
As most individuals who kill Tieflings in the grove aim for an outcome where they don't make it safely to Baldur's Gate, the chances of someone discovering this through a regular playthrough are remarkably slim. Nevertheless, it demonstrates that Larian truly wanted to take every decision into account and prevent players from getting stuck or blocking themselves.
As I mentioned before, however, Larian is not here to hold your hand. If you make truly foolish decisions, such as allowing Gale to explode, you will simply receive a Game Over. The same can happen if you manage to get yourself killed before recruiting a sufficiently large group, which is rather easy to do at the beginning if you're not careful.