WoW Retail: Leveling 20-50, NPC Army To Fight For You (Patreon)

The Mists Of Pandaria, Kun-Lai Summit quest "Instant Courage"

.https://www.wowhead.com/quest=30601/instant-courage

can be exploited to create a small army of npc's. 

Create a party (this can be with a starter edition account you own) and convert it to a raid group.  Click on all the barrels located in the quest area, this will release grummies which will then fight for you. Because you are in a raid group you do not contribute to the progress of the quest and can keep creating grummies. 

The quest requires level 20. The npc's scale with you by level up to 50, with MOP timewalking.

The quest has two pre-quests both of which are just breadcrumbs. Talk to Lorewalker Cho at One Keg, then follow his quest to the next npc, accept and turn-his quest to receive "Instant Courage".

Your npc army can get very large, but not of infinite size due to the fact each npc expires after 5 minutes, however you can easily spawn enough of them to kill any hostile mobs in the area with this trick.They will follow you anywhere in Kun-Lai. 

The npc's are also invincible, for some reason. 

To level optimally with this trick it is best to combine it with rested experience and the heirloom bonuses introduced in Shadowlands.