The way I always saw it is that in canon, the New Light mission in D2 is a prequel to the whole thing (D1 included) to act as a tutorial as well as to show how your guardian came to be. Obviously, D2 is a different game from D1, so in D2 you don't get to play through the D1 stuff after you're born as a guardian, but you're still the same guardian in lore from D1. I'm not sure if I'm getting my point across properly, but basically what I'm saying is that D2 New Light is the exact same New Light in D1. New Light (D1 and D2) ---> D1 (after New Light) ---> D2 (Red War) ---> D2 Expansions in order As you can see with that, the story/lore of the games up until now has not changed at all, but you just don't get to play some of it as a new D2 player. You play New Light to show the very beginning of the whole story and then are fast-forwarded to the present. As for the question about changing up canon, I assume that this new mission is just replacing New Light. It'd be neat if they also switched it out in D1 to clear up the confusion. I could be completely wrong about this part, but it's the only way I can see it making sense.