Portal Storm:
In the aftermath of the Resonance Cascade at Black Mesa, Portal Storms occurred all over the world bringing forth life forms from Xen. This peculiar phenomenon is generally capable of inflicting severe structural damage to objects, such as buildings and bridges. A Portal Storm consists of a blue "wave" which resonates from a source portal and moves across the landscape, negating gravity as it goes. As a result, any object in its path would suffer damage from the brief weightlessne…