You will encounter some challenging puzzles in your TFS playthrough, and the Exegesis puzzle is one of them. To complete it, you first need to know how to make light motes in Destiny 2: The Final Shape.
Where to find light motes in Destiny 2 The Final Shape
There are two types of motes you will need to find in Destiny 2 The Final Shape: light and dark. Dark motes are easier, as all you have to do is defeat the 'Eater of Light and Darkness.' You'll find plenty of these Hive Knights in the area where you need to complete the puzzle.
Finding Light Motes in The Final Shape expansion is the tricky part. You still need to kill the 'Eater of Light and Darkness,' but you need to do it with the Relic Shield (Captain America style). To use the shield as a weapon, press R1 on the controller or C on the mouse and keyboard.
Once you have gotten the motes, you will need to place them in their corresponding fonts, light to light, dark to dark. The Exegesis puzzle has four fonts to match up: two light and two dark.
You'll encounter the light and dark motes again after the main campaign in the Destined Heroes exotic quest. However, there will be a slight change to the mechanic here. To get light motes, you will need to kill the 'Eaters of Light,' and to get the dark motes, you will need to kill the 'Eaters of Darkness.' Instead of matching light to light and dark to dark, here you will switch it up and take light motes to the dark fonts and dark motes to the light fonts.
Once you've got the hang of collecting the motes, it shouldn't be too difficult for you to complete all the puzzles that use this mechanic in Destiny 2 The Final Shape.
If you are stuck in other areas of the game, you can also check out the Destiny 2: The Final Shape Dial Puzzle Guide or How to solve Glyph puzzles in Destiny 2 The Final Shape on Pro Game Guides.
