The otherworldly Harbinger channels the tremendous and unfathomable energies of Outworld Crystals, found only at the rims of the Void, into the world of mortals. Periodically yet temporarily, the complex forces reverberating between these crystalline conduits attain an improbable sort of resonance whose magnitude spontaneously overwhelms the prismatic power Harbinger consciously wields - sending a supernova of energy surging through a critically empowered Outworld Destroyer. Skybourne with unimaginable power, rivaling the cosmic forces responsible for creation itself, Harbinger's inauspicious presence reaches untold heights.
Perhaps this brief but undeniable manifestation, whose duration becomes increasingly more frequent and stable, is a foreshadowing that the imminent danger that is feared to follow the Harbinger, is actually Harbinger itself.

http://www.polycount.com/forum/showthread.php?t=107837
Part of the Polycount/Valve Character Set challenge.
Description by the wonderful Strange