The Army of Light and Argussian Reach are new factions, introduced in 7.3 patch. The only way to get exalted with them is to complete daily local and weekly quests. It’s a time-consuming and hard work: you should be online every 6 hours waiting for local quests updates and then do every single Argus quest.
Army of Light reputation benefits:
- infinite Augment Rune, the important consumable for every mythic raider
- the gorgeous light-theme mount “Lightforged Warframe”
- a tabard
- profession recipes
Argussian Reach reputation benefits:
The main advantage is a Krokul Flute – the analog of Flight Master’s Whistle, a helpful feature in a non-flying Argus zone.
The others are:
- some profession recipes formulas
- 6 recolored Ruinstrider mounts
- shoulder enchant that provides to collect veiled argunite from enemies