With the help of a wonderful summoned spirit last night I cleared through blight town and finished the spider boss.
Then with a helpful message I found the hidden spider and bonfire, joined the chaos covenant.
But before I turned the game off to go to bed I went a tiny bit further to the next area with all the egg carriers laying around. I questioned if I should kill them, but went ahead and murdered a couple, also slaying those adorable little maggot things that come out.
So by killing them did I just screw myself out of the covenant? Can I rejoin the covenenant? Still use the bonfire?
I kinda wanted to get the pyro spells she offers, but I guess I can always get them on NG+.