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This page is based on information from the Dota 2 Dev Forums (this thread). I'll go ahead and transcribe the post below if you don't have beta access.
Lore In Progress:
When the World was still a cooling blob, it captured an eerie companion--a glowing crystalline sphere that came to be known in lore as the Mad Moon. This small orb was full of violent radiance--a visual reminder of conflict in the heavens, bright enough to compete with the sun in daylight.
But the Mad Moon was no inert rock. It was more truly a prison, in which two warring ancient intelligences had been captured and flung into exile aeons before, once the vast Primordials that underlay creation had tired of their endless strife. The punishment for these Ancients was to be locked together in one form, forever falling through infinity...and thus it went until our unfortunate world captured that wanderer.
For ages, primitive societies rose and fell beneath its weird glare; creatures of varying intelligence and sophistication gazed up in wonder and curiosity, to whatever extent their sentience allowed. Meanwhile, orbital stress and tidal forces allowed the Mad Moon's inhabitants to begin exploit what were at first the slightest of weaknesses, as they set to work prying open their prison. The cracks spread slowly, from the tiniest fractures, until at last there were millions of fissures, vast and aglow with weird energies.
On one apocalyptic night, the moon finally shattered, torn apart from within. Most of the moonstuff was flung into space or consumed as it hit the atmosphere. A few rare fragments fell to earth, either as fused molten lumps or as jagged crystals. The shards lay where they had fallen, and gradually the land around them recovered. As the survivors of the prehistoric cataclysm recuperated, flourished and developed civilizations, the Mad Moon became less a memory than a dream, with the night of its destruction woven into their myths.
The fallen shards of primal matter had fractured into their original composites: Radiant and Dire. In its pure form, each type of stone gave off a peculiar energy. For those who settled around the sites, they found themselves feeding on this unearthly power until they had not only harnessed the energy but made themselves dependent on it. They built shrines around the Ancients and revered them, ironically, as godlike entities that had fallen to earth.
The Ancients, both Radiant and Dire, provided many benefits: kinetic energy, mana, protection, even resurrection. But the emanations changed everything in their influence. Around the Radiant, the effects were bright and colorful, evoking lightness and charm. Around the Dire, a sinister radioactive glow, a visual seepage indicative of poison and decay. Neither force was neutral; they were both perfect complements and total contradictions that could never be at peace.
As each stone's cultural influence spread, it eventually came in conflict with the societies of its rival. Interference between the Ancients was cause for war, as the presence of one caused a corresponding fall-off in the energy of the other. Each stone could only be restored to full power with the destruction of its Foe-stone. And so the enthralled creatures rallied to protect their land by destroying the neighboring Ancient, and from far and wide the Heroes heard the call to battle and came to join, hardly realizing that in some sense both sides were the same.
For all this time, the Ancients had been patiently working to resume the timeless war that had been the cause of their initial banishment. And as Heroes from all over found themselves drawn into the fray, none suspected that they were taking part in the ultimate battle of a conflict that had raged since the beginning of time.
This lore underlies some of what appeared in "Tales From the Secret Shop" comic...it normally wouldn't be exposed outside of actual storytelling, but since people want more insight and the ability to comment on the lore in progress, I'm posting it here.
This is currently WIP. It was posted yesterday (which is 11/21/2011) and should be relevant for a bit until the next revision. -Lancey 22:02, 22 November 2011 (UTC)