A Siphon is an Illyrian magical jewel gifted to warriors with the power to give them an advantage in battle. They filter raw power and allow the user to transform the power into different objects, typically shields, weapons or armor. This object manipulates magic to be more precise. Siphons don't contain an infinite amount of power and can run out. To use a Siphon, the person's power must be compatible with it. For instance, Rhysand is unable to use a Siphon, as his power overloads the Siphon and causing it to shatter.
Siphons can be a range of colors, and this color will be the color of the desired object, that a user can make with the Siphon. Although most users wear one Siphon, Cassian and Azriel are shown to wear multiple.
- The objects are named Siphons as they are able to channel the power and even empty it if necessary.
- When an Illyrian takes part in the Blood Rite, they are not permitted to use any magic, including a siphon.
- In the real world, a siphon can also refer to a wide variety of devices that involve the flow of liquids through tubes. 
- A Court of Mist and Fury (First appearance)