A Vortex of Discord is an exceptionally difficult magical construct to fashion, requiring the mastery of at least two different elements by the same caster. Naturally, since most elemental magic-users focus only on a single element, they are both unable to create such a Vortex and end its influence upon them - an outside party is required.
As the name suggests, Vortex of Discord creates intense strife between any elemental magic-users who study the elements employed in the Vortex's creation - thus, the use of fire and water would cause all fire and water elemental magic-users within a huge area to bicker and argue incessantly, gradually turning to actual violence and even murder.
Every Vortex is different, depending entirely on the elements used to create it. For example, the Vortex used by Ziraphelis to divide Caltarelair and Remishaz, thereby preventing his former colleagues from uniting against him when he succumbed to Evil, was fashioned out of their respective elements of earth and air, and took the form of a great whirlwind bearing huge rocks. Other Vortices would undoubtedly be different.