The Dark Urge is easily the Baldur's Gate 3 origin character with the most mystery-shrouded past. The likes of Wyll, Gale, and Shadowheart might have their secrets, but the game's final 'Origin Character' takes the cake - and it's a tale its director has wanted to tell for a long time.
While Baldur's Gate 3's other main characters have predetermined appearances, classes, and personalities, the Dark Urge is different. No matter whether you roll them as a Dwarven Warlock or a Dragonborn Barbarian, their story will remain the same - and it's a very gruesome story. There's a serial killer lurking the Dark Urge's past, but you don't remember them. All you know is that you still have their urge to kill, and you'll have to learn to deal with that.
In an interview with Play Magazine, game director Sven Vincke said that he's wanted to tell this story for a long time; "I always wanted to do a story about a serial killer that didn't remember being a serial killer." It wasn't until BG3's writers got their hands on the idea for the Dark Urge, however, that it began to come to life; Vincke says that "the writers embraced it, [making] it a much, much, much more [original story]."
The Dark Urge remains shrouded in mystery, and what we've heard about the character so far suggests it'll take quite a lot of piecing things together to work out the darkness in their heart. Vincke implies that it might not be until we reach the titular city at the game's heart that we get a final answer, pointing out that your trip to Baldur's Gate, a city once terrorized by the god Bhaal, Lord of Murder, certainly makes for "an interesting combination."