Shivers are Silvers who can decrease temperature. However, their ability isn't limited only to freezing and frost inducement. It also seems they possess the ability to move ice and snow around. For example, they are capable of turning moisture into ice spikes and throwing walls of them at a time. They are immune to cold.
"Shivers are elementals, manipulators of temperature and cold, able to freeze things dependent on properties of the target. Most shivers can easily manipulate water or more stable liquids into ice." - On Silverblooded Abilities by Victoria Aveyard