I have seen several occurrences where players have a nearby Luminopolis Outpost's NPC in their cornerstone. This can be unfair to other players due to the fact that nobody except the cornerstone's owner can alter the cornerstone and that player can prevent others from using the NPC. This can also be used to automatically farm an Outpost NPC (such as Kami of Fiery Fervor's "Defeat Enemies in Luminopolis" for Invaders and Kami of Considered Compassion's "Defeat a Rampage Boss" for Rampage Bosses).