You would probably start the game out with this gesture in the next souls game, or learn it from someone like Solaire. Basically, the player would initiate a gesture where he would extend his right hand in front of him. He would then be stuck in this pose for about 7 or so seconds (if damage he would be put out of the pose, or maybe he would simply move out of it). During this time, if a dark spirit has invaded, or the host has summoned a phantom, they too would also be able to use this gesture. When facing one another and using the handshake, they would lock into a 3 second pose where they would both shake hands, and then retract there hand to there sides to be able to move again. You could also have it as a different type of handshake, fist-bump, brofist or whichever the developers and players find most appealing. This taunt would be used as a sort of new form of bowing before a pvp match, or a way of greeting a phantom when they are summoned to your world.