Evoking

What the Evoking Heart Aspect does when broken, spawning Vexes that defend you is not what makes it special. Rather, its oddity lies in how you obtain it. Simply crafting it is not an option, as the Evoker is very secretive about how its magic is performed. So instead what needs to be done is giving a Blank Heart Aspect to an Evoker who will then convert it to an evoking one.

This process is of course not without risk, considering that Evokers tend to be quite hostile folks. However, staying out of their sight long enough should suffice for a quick conversion.