If our human's feelings got too strong then it'd become hard for us to take form.That is not just limited to us, but also to the Abyssal ships.The so very heavy wishes can not be grantedIt's the same reason why those like Nagato are hard to be dropped compared to others.
Drop is the provided reading for "invoked", as in invoking a god to possesses someone.From then on, until now, as people's feelings get deep and complicatedly more and more piled up
