Comments posted to our Dark Souls 3 Wiki
I really wish the giant would shut up. sick of waiting around just to die.
I think I just encountered a glitch, I was cooping at the Ringed City Streets, I had the way of blue covenant equipped,

I put down my sign near the bonfire waited for a bit and for some reason I was summoned as the boss for this boss fight, I haven't killed that dragon yet, so I can't join the covenant, is there some kind of hidden mechanic I am not aware off? or just a freak occurrence?

Thankfully it was just one guy, I beat him because he didn't even try to kill that first painting guardian.
Being summoned to the boss fight by placing your sign is possible, it just happens on very rare occasions. It happened to me, too.

I think I also read somewhere here in the wiki that you can be chosen as a Spear of the Church when using the Red Eye Orb, but I can't confirm that from my own experience.
You're wrong; if there is no available Covenant member, it picks an online player at random.
So do you get a slab each time you reset the boss and beat it or is it just the first fight?
No, you get only one per Playthrough!
Well I beat the boss but the player that got sumind was a lag *** and I killed him and now im stuck in the boss fight with no enimys
Is there a way to get Halflights Armor?
Halflight uses the Antiquated Plain Set, which is found in a secret area before the boss fight (see wiki).
I've been summoned several times as a boss while leaving a sign on the floor.
Leaving your sign down makes no difference.