purple phantoms is boss!! again! farming soul will fight

If these are the main invaders, can't want for more info and to join.

I just hope they dont have a terrible arena meta

purple phantoms is random?

How do you join this covenant?

Before defeating the Rotten Tree boss go to the Undead Settlement starting area bonfire. Keep going right pastt the rooftops with the tiny pointy hat assasins and drop down where you will find an enemy with a cage on his back. Approach from behind and press "examine". A cutscene will appear and you will be teleported to the area where an NPC gives you the covenat. DO NOT defeat the tree boss before triggering the cutscene otherwise the covenant is gone.

Walk back to where you fought the boss at and you may see a summon sign on the ground (you do not have to be embered to see it) that will summon you as a white phantom into an arena with Sirris of the Sunless Realms. Beat the NPC there and you'll get the covenant item and unlock the trophy for the mound maker's covenant. Video:

The NPC you need to summon only appears after you've advanced far enough in her questline. It's the Darkmoon Lady.

It would've been great if you could help killing bosses, this is defo a downer.