From the Wiki:
"...most of the battles between large factions involve insane chainsaw action with each side sending its hardest units to battle the other's, OTCs in hand. The awesome results of these battles are massive explosions of violence and blood which go down in the books of BrikWars legend."
Original OT is very hard to come by. So some enterprising souls with more brains than brawn set out to make their own. It was theoretically possible to manufacture OT since the original supply was minimade. They devised a plan to scour ancient legendary battlefields for microscopic bits of OT that may have been knocked loose in the OTC vs OTC battles. After thousands of years of searching, they found it, a single atom of OT.
Now with an original OT sample they could begin the scientific process of cloning it into a larger usable supply. It took over 100 million years to discover the best mixture of chemicals, power levels and environments that would grow more OT. They eventually got the process down to 1 million years to make enough clone OT to make 1 chainsaw. The trick was that each mass of clone OT needed 1 atom of original OT at its core. The self repair properties of OT took care of the rest. The atom of OT would scavenge the adjacent materials to clone itself, this is a slow process. The resulting clone OT is inferior to the original, but anyone who actually knows the difference first hand isn't talking.
Ancient Battlefields are now a source of conflict among those factions who wish to clone OT. Each atom of OT an explorer finds and sells at auction or to a private buyer could buy him a planet. Although a minifig could spend his entire life searching and still find nothing.
Of course there are still mad scientists on isolated moonbases that are running experiments to recreate the conditions that produced the original OT. None have been successful. I suppose thats what makes them mad.