The Nocturne Triumph is something that players will need to complete in Destiny 2 if they want to get the Splicer title. The Splicer title is the seasonal title for the Season of the Splicer, and will only be awarded to players who take the time to complete all the relevant Triumphs. They will then be able to display the title in-game.
To complete the Nocturne Triumph, players will need to collect all ten pages of the Beneath an Endless Sky lore book. To get each page, a story quest will need to be completed. All the quests are largely linked together, so finishing this one up is really just a matter of logging in on Tuesdays after the reset and finish the new quests that will be available.
One page will be earned by complete the Beneath the Great Machine quest that begins the seasonal story content, eight pages will be earned by completing the various Path of the Splicer quests each week, and the final page will be earned by completing the As Prophesied quest.
The final quest, and page, will not be available until we get close to the end of the season. Players will also need to go into the Triumphs section, find the lore book under the Nocturne Seasonal Triumph, and interact with each page to “add” it to the book for them to count.