Every decision you make in Baldur's Gate 3 has an impact on your journey. Even your decisions during character creation.
The decision of which of the 11 races to play is hard enough, and that's not to mention all 31 of the subraces. Depending on that and the decisions you make during your journey, NPCs and your companions will perceive you differently. Each of your choices will have an impact. The consequence can range from merely an NPC not liking you anymore to one of your companions dying, to a whole city being doomed or even worse. And Larian Studios will give you the option to be the worst version of yourself.
The Dark Urge
The Dark Urge is portrayed as a Dragonborn with white scales and is not available during early access. With launch, you will be able to customize this Origin Character to your liking – even a half-orc with a bongo, as Larian Studios suggests. While all the Origin Characters have their unique history, background and dialogue options, the Dark Urge comes with an extra on top of that.
After Dark Urge lost their memory on board of the Nautiloid, they are accompanied by Sceleritas Fel, a vile and loyal servant who urges this Origin Character to the most violent acts possible in the game. Ripping off hands and kicking innocent, cute little squirrels are two already known examples of the intrusive thoughts Dark Urge will have. But if you resist or engage these urges is again up to you.
Starting at 4:36:18 you can get a first impression of what you should expect if you choose to play as Dark Urge (or however you'd name that character).
If you should choose not to go with Dark Urge (on your first run, admit it; we all are gonna play as a murder hobo at some point) they won't join you as a companion, but the devs hinted that there could be an encounter with them as an NPC.
However, if you should choose to play as Dark Urge, you still will have the chance to form relationships with your companions and even a romantic one with a "patient paramour". As Larian Studios said; while there is darkness lurking inside Dark Urge, the decisions you'll make form the world around you. There is no good or evil. Only choices.