When the Burning Legion conquered Argus, the eredar, led by Prophet Velen and the naaru fled to Azeroth. However, several eredar remained behind, vowing to continue fighting the Burning Legion. Having defeated Gul'dan at Nighthold, the heroes of Azeroth return to Argus to take the fight to Sargeras. There, they encounter the Argussian Reach, a band of eredar that have dedicated their lives to battling the Burning Legion.
Finding and killing a rare elite anywhere on Argus will reward a small reputation increase.
New to Legion are the concept of world quests. There is no limit on the number of world quests that can be done per day. When world quests expire, new world quests take their place.
There are three separate seat of the triumvirate quests that reward 250 reputation points each.
The Argussian Reach Insignia is a reward for certain class hall missions.
7th Legion world quests are available after you hit level 120 and complete the quest Uniting Kul Tiras. 7th Legion world quests are any world quest that is completed on Zandalar. You can complete any number of 7th Legion world quests each day. Each world quest has a timer indicating how long it is available. Once it expires, a new world quest will take it's place, whether it has been completed or not.
There are two weekly quests that are worth 1000 reputation points each. These can be completed once per week. One quest requires you to collect pristine argunite. The other requires you to complete three invasion points.
Greater Argussian Reach Insignia can be found as a bonus reward for having more than 100% chance to complete an appropriate class hall mission.
The Demon's Soulstone is a rare drop from elites found on Argus. Using this item will grant 1000 reputation points to ALL Legion factions.
When the Argussian Reach Emissary Quest is available, complete four Argussian Reach world quests within the allotted time (generally 2 days). Doing so will allow you to turn in the quest to Toraan the Revered located on the Vindicaar. A new emissary quest is available each day.