Vertex is a stereo VCA with some clever tricks up its sleeve to give you more control over the stereo domain. Vertex contains four analogue VCAs configured in such a way as to give you voltage control of the amplitude of a stereo signal (or make a mono signal stereo) as well as having control of the balance or panning of the signal.
Easily patch up a stereo signal path with a single envelope generator, skew your stereo image or pan a mono signal with CV. Vertex also takes advantage of the VCAs used to be able to saturate at unity gain without distorting your audio signal. This means that you can waveshape an AD envelope into an AHD using the Skew control to add punch to your patch, and use the Skew CV to dynamically alter the envelope timing to change the relative loudness between the Left and Right signals while still keeping the peak signal levels the same.
Vertex is also a great tool for controlling the dynamics of an XY signal for oscilloscope or vector laser patches.