If you use a Cracked Red Eye Orb, you'll be unable to affect the world.
If you put down your summon sign, you will be drawn in their world as if an ally, letting you kill enemies and the player alike. However, what makes this covenant unique is that you can also affect their world in other ways. The goal of a Mound Maker is to join another person's world and kill them and/or any other phantoms (regular white phantoms, Warriors of Sunlight, Watchdogs of Farron, Aldrich Faithful, Blue Sentinels, Blades of the Darkmoon.
