Sooo, had a strange glitch today.

I dropped my sign in the cathedral, ready to Sunbro it up against the gargoyles, and after a minute or two i get the text "Invading world as a phantom."

Somehow, i got sent in as a BP. IDK if it happened when he summon me using my sign, or if it forced me in somehow. Either way i tried to help by blocking enemies into a corner and such, then letting him backstab me.

Has this happened to anyone else? Is there possibly an item i have/am equipped with that causes this?