Truth is a staple Rocket Launcher that originally appeared in Destiny 1. Its exotic perk, Prototype Trueseeker, causes rockets to aggressively bend towards targets before detonating within proximity. It's extremely accurate, basically, and a lot of fun to use. It's not too hard to get either if you're comfortable traversing the Dreaming City.
Here's how to get Truth in Destiny 2: New Light.
Complete a Menagerie event
A pop up message on login has alerted Guardians that Truth may be found in the Menagerie. Grab your Chalice of Opulence and complete a Menagerie run to obtain the quest item (an Awoken script) from the final chest.
Then visit Petra in the Dreaming City to move onto the next step.
Complete an Ascendant Challenge bounty
When you meet Petra grab that week's Ascendant Challenge bounty and complete it to get four pieces of a shattered map. Right now, on the day the Truth quest dropped, there's a bug that means you only have to find one map fragment and buy the rest from Petra. This will probably be fixed soon.
The fragment locations are described in cryptic terms in the 'A Map Asunder' pursuit description, and they seem to vary from player to player. Below we've listed some of the challenges we've seen so far.
Note that when a step requires to be 'Ascendant', that means you need to swig Tincture of Queensfoil. These drop from Ascendant Chests and challenges in the Dreaming City.
To decode this map piece, complete Nightfall strikes while influenced by a Power handicap of 100, and also use Rocket Launchers to defeat enemy combatants in Nightfalls.
To decode this map fragment, find the badge of a Downed Corsair in the Dreaming City and return it to any Corsair outpost.
While Ascendant, defeat combatants on Nessus using any Rocket Launcher. Multikills grant the most progress.
Defeat Hive on the Tangled Shore. Defeating challenging Hive grants the most efficient progress.
The community is still discovering all of the possible map fragment locations. Some are hidden behind jumping puzzles. On YouTube WoW Quests has made some very helpful videos showing some map fragment locations.
Dreaming City map piece
Cistern on a Centaur map piece
Child of Darkness in the Tangled Jetsam map piece
Badge of a Downed Corsair map piece
Complete the Warden of Nothing Strike while Ascendant
Finally, glug a Tincture of Queensfoil and launch the Warden of Nothing strike. Players have noticed relics scattered throughout the strike which extend the end-of-mission timer long enough to complete a jumping puzzle in the final room.
Redditor BoSolaris has snapped images of six relic locations. It sounds like there are more hidden away in the strike, but you don't need to discover all of them to extend the end-of-mission timer. BoSolaris' video below shows you where the platforms are at the end of the strike.
Finally, take the rocket launcher to Werner 99-40 on Calus' barge on Nessus to complete the quest and enjoy those homing warheads.