The real shame about Gravelord Servants is that you can only infect worlds that are in NG+. Adding extra enemies to a world is a brilliant mechanic, and I wish it had more actual use.
Luckily, if you play on PC (PTDE) you can use mods and activate gravelord enemies for your own world even if you can’t reliably infect someone else’s world. Better than nothing, and adds something different to the game for people who have seen it all.
For anyone that doesn’t know what the covenant is about:
Joining the covenant gives you an online play item that infects another player’s world by adding red phantom versions (extra difficulty) of certain enemies in the area they’re in. The player can find your summon sign, which moves and follows your position, and they can enter your world to PVP you for the chance to clear their world of the curse.
Really interesting mechanic, but only works in NG+. By the time you hit NG+ you could be any level, when you combine it with online play only working within a certain range (around 10% tolerance of your level, so 90-110 if you’re SL100) it vastly reduces the viability of the covenant.