Vyn priests will spend an incredible amount of time increasing channelling and soul depth knowledge. In many cases far more time then the other types of priests.
For this reason I chose the Path of knowledge Knowledge since it contains bonuses from faith level and if you reach a high meditation level you also gain an additional 25% permanent skill gain. This path also protects against skill loss on death.
==== Fo ====
Fo works with animals and crops. For this reason I chose the Path of love Love for Fo priests. The ability to enchant grass is a very useful one that comes at a relatively easy meditation level to attain.
==== Mag ====
Mag is about mining. Path of power Power provided the ability to turn a tile (even an ore I believe) into lava and then later freeze that tile back to rock. This is a great option to have if you will be mining tunnels, cave canals etc.
Some people choose path of insanity for more warlike Mag priests. I understand Shield of the Gone is a very compelling reason for choosing this path.