I've been thinking how weird it is how bondsmith spren can just make or conduct various forms of investiture come into the physical realm. I think they might be Spren of the spiritual realm, first off the investiture itself is of the spiritual realm so them manipulating something not of the cognitive realm is weird. Second the Nightwatcher can do some kind of trickery with connection though I may be wrong since it seems everything attributed by the Nightwatcher was actually cultivation. I have feeling that when the gods of Roshar made bondsmith spren and unmade the took creatures from the spiritual realm and made them or unmade them so that they could experience the physical and cognitive realms. what do you think? Also since all things in the spiritual ream exist as one, it isn't weird for them to be as different as they are as bondsmith spren because the are probably like given more individual identity out of the spiritual realm.