One of Pantheon’s tenets is ‘Engage the World!’ When we talk about being a PvE MMO, our definition of ‘environment’ means a lot more than just fighting NPCs -- players will be contending with the world itself. Some regions will be very hot or cold. Some areas within a zone might be enchanted with complete darkness, or silence (meaning spoken spells won't work), or poison or miasma. Small tornados could travel through a region, compelling players to work their way around them, not through them, lest they take significant damage. Also, certain spells may work better or worse (or even only work) depending on the climate or atmosphere -- for example, a 'Call Lightning' spell could deal more damage than a typical ‘lightning bolt’ spell but could only be cast if there is a storm in the region.