There are a ton of questions surrounding the lore of Destiny. Bungie filled it to the brim with all sorts of secrets and hidden information tucked away in nooks and crannies of the game. However, one question that hasn't been answered in the original game and won't be answered in Destiny 2 is what the Darkness actually is.
In an interview with Game Informer, game director on Destiny 2, Luke Smith, explained that the upcoming sequel won't be exploring what the "Darkness" actually is...
To be honest, all of the terminology in the original Destiny just seemed really moot to me. During the missions, none of the game's lore really shined through in the actual gameplay, and this resulted in a lot of the missions seeming completely disconnected from whatever world-building Bungie was attempting to architect for Destiny.
It was a far different experience than Bungie's previous narrative-driven shooter series, Halo.
In the Microsoft-owned franchise, there was a lot of lore that was thrown at the player during the actual gameplay. Discovery and narration -- oftentimes from Master Chief's AI sidekick, Cortana -- helped give gamers an idea of what was going on, why, and what sort of actions they could take that would affect the world around them.
Bungie did a pretty good job of condensing all of the important parts of the lore within the Halo universe into the actual campaign modes. It made it easy to follow and enjoyable to play through. It also probably helped that the developers were crafting a single-threaded narrative through the lens of Master Chief and Cortana, as opposed to the nondescript, mostly blank player-created characters in Destiny.
In a way, the narrative exposition for MMO games usually has to be pushed off to the side or told through cinematics before or after the mission with very little involvement from the player because it has to include every player in the group on that mission. So for games like Destiny, the more singular focused narrative and deep-dive into the intrigue and mystery of a game's lore has to be put on the back burner to compensate for the multiplayer element.
For Destiny 2 the team has attempted to rectify the problem by including more cinematics, dialogue and interactions with other characters to help tell the story about The Light, and Ghaul stripping the player character of their powers.
For the sequel, the core story is like a tale of retribution, as the player character will have to start from scratch to regain their Light and their standing as a Guardian while attempting to defeat Ghaul. The Darkness, as a story thread, will be pushed to the back of the line for now, and it sounds like it won't be making an appearance or get any thorough exploration within the Destiny universe until the third official game comes around, or maybe further down the line as part of an expansive story add-on.
Anyway, gamers will be able to experience the fight for the Light in Destiny 2 when the game launches this September for Xbox and PlayStation consoles, and in October for PC.