Army Diffusion Barrier

The single spell singlehandedly responsible for how the wars are conducted between countries. The ideas used in this technique are rather old, so the it is not a single spell, but rather a family of similar spells constantly developed by every country to give them even the slightest edge over the enemy. No army can confront a magic wielding enemy without this barrier deployed, so maintaining is is the most important task of Army Magicians.

The idea for this spell originates from the fact, that most people are very weak and easy to kill. Whether it's concentrated sunlight or an easy to create poison gas, soldiers could die in thousands without ever coming close to the mage. That is no longer true for trained knights or wizards, but armies require protection from that type of attacks - lots of harm done with little cost in mana and resources.

Army Diffusion Barrier is the most optimal solution found by archwizards researching the topic. It attempts to spread the incoming attacks over the whole army and weaken them very slightly. It doesn't react to anything beyond a certain energy level as to not tire the arcanists maintaining it. This method makes the barrier very easy to maintain for prolonged periods of time - most armies have them deployed even when marching to defend against ambushes. While the casting of this spell is not easy, it has been streamlined and standardized so it can be taught and practiced to perfection even by relatively inept magicians. 

Effect

Diffusion of low energy attacks over a large number of soldiers, essentially preventing them from affecting the army.

Material Components

Requires multiple casters spread over a distance of at least few dozen meters.

Gestures & Ritual

Casting of this spell involves continuous synchronization of the Weave with other mages casting this spell.