Sorry to the dude out there - I thought the white thing on the ground was loot and just mashed the button. I'd heard of invaders and when your ghostly white self showed up, I went to try and fight you, rather than perhaps the assist on the boss battle you were expecting!
Not that I killed you, or even scraped you - quite the opposite!
But it may have been disconcerting!
I think I saw you again latter in another summoning circle.
I think I'll attempt the tauros demon thingie solo a few time more, in penance, before I consider accepting a summoning circle.
I didn't even know summoning worked that way - I thought you had to start it, not that someone else could make a summons offer itself in someone elses world?