Huginn is referred to by Josho as the paramount technique of Shape manipulation.
It may only be used when Josho has access to the energy contained within the Rashomon gate. It is used with another jutsu, for Huginn's effect is to allow the user to manipulate the form of anything in their reach, though the distance of the object affects the power needed to use it, as does the energy of the object. The energy from the Rashomon is used as a solder or catalyst. Other things may be imbued with this energy, making for powerful weapons. This allows for spears made of rock, and inventive uses for jutsu, even the enemy's, if their chakra control is poor.