I don't think the tentacles are reducing the enemy attacks by one. Against both a skaven and a vampire they are still getting four or five attacks on their turn. I actually have two Possessed with tentacles, don't know if they are meant to stack but that certainly isn't happening.. Would be nice if it did happen that way! Off-topic, it would be nice if the requirement was lowered for the skill which reduces enemy armour; strength 55 can't even be reached if you haven't carefully picked your brethren for his original strength! Going up against vampires and heavily armoured enemies is very annoying..