Originally Posted by Seano
I don't think it works unless there's some trick to it that hasn't been shared yet.
I just read up on it and apparently you must be human AND the person summoning you must be actively in the Way of the Blue and have the Blue Seal equipped. So for this to happen all of this must be in play:
You human, active in blue sentinel covenant, have the guardian's seal equipped
Them active in the way of the blue, have the blue seal equipped, be invaded and on the same server as you and same soul level range.
It probably works fine but it's probably so damn rare to have all of these conditions met. Shit I haven't even been invaded once in 15 hours of play time.