A Primer on the Great Downward Engineering Company

Founded in 957E, Maybeth's Great Downward Engineering Company was formed to support the newly created Glodsson Heavy Industries. Arik Stonecleaver, the brains behind the "Great Companies" project imagined that GHI would worry about construction and logistics on the (relatively) safe surface, while MGDEC would help build mines, and scout for valuable and (relatively) safe resources underground.
The Great Companies project died along with the waning fortunes of the Valley. There just wasn't enough money for the kind of projects Stonecleaver envisioned. Ultimately, most of the companies would wind up the property of each of Stonecleaver's Partners. With the death of Mirrax Olivia, Mirrax Marines would shut its doors for nearly half a century. GHI would be sold to Glodsson, to hopefully allow the dwarf to recover some of his losses in helping Stonecleaver set up the company. Ironclad Goods and Transport would remain operational, although Izchak's Magical Goods and Services would shut its doors forever.
As for the MGDEC, it had nothing worth liquidating, and was formally handed over to Maybeth in 961E. As long as she was still doing something that resembled the original charter, Maybeth Calaelen could still reap the biggest benefit of the Great Companies project: She would pay no tax on any income the company made.
To her credit, Maybeth relocated the company to the area that is today Tarren's Junction, to help the mining outpost set up lucrative gem mines in one of the more dangerous parts of the Valley. She would subcontract people who knew how to build a mine, while she and her mates would adventure. They would clear the area and keep it safe, but they'd also check that the mine didn't open out onto any buried temples or ancient ruins. Just to be safe, of course.
It was here that the soul of the company was first forged. While admittedly the company was actually doing a pretty great job of engineering things in a downwards direction, most people knew it as Maybeth's adventuring party. 
Maybeth herself was an odd one, a child of an elf and a dwarf. In those early days, MGDEC would set a lot of precedents. They found treasure, fought undead creatures, and even caught the attention of the gods. For her work recovering an ancient dwarvern helmet, she was blessed by Torag, god of battle (and the same god her father had served as cleric). For her work, she was named Favored of Torag, and granted the title "Bladestorm". 
Tragically, in the early weeks of 963E, she found a cursed sword. According to her friends, the sword told her of a lost queen and her family, deep within the Dark Halls (which would be later known as Rappan Athuk). The sword whispered to her, begging her for help, telling her stories of loss and pain. She sold her company to Stonecleaver's son, liquidated every other asset she owned, and then borrowed what money she could. She spent this money hiring more adventurers, and outfitting them all with the finest gear she could afford. Then, the entire remaining crew of MGDEC set off towards the Dark Halls, and never returned.
From there, the ownership of the company took a circuitous path. The combined asset of the Great Downward name, and the land rights to a moldering fort (Castle Calaelen, built by Maybeth's mother) in the middle of nowhere theoretically held value, actually extracting that value was much harder.
Arik Stonecleaver would fall on the same hard times as his father, and sell the deed to the Skorrian noble (and pretender to the royal line) Jezabel Mabel IV. When her play to take control of Skor cost Mabel her fortune, she would lose the deed and the last of the money to clear a gambling debt with a dwarvern crime syndicate headed by the infamous Argent Ironhand. He too would fall upon hard times, and would sell the deed to Jackboot the Pirate in exchange for helping him flee the Valley. 
From there the pattern continued; the deed would find itself in the hand of someone who thought well of themselves, only to have them fall upon hard times and be forced to pass the contract along. Way back when the companies were founded, an insurance measure was put in place to ensure the deed would never be totally lost. A magical legal company (by the name of Bent and Twiss) was charged with making sure the contract passed to its rightful owner any time it was mislaid.
Finally, in 1789E (over 800 years since Maybeth's disappearance), the contract found its way into the hands of Pezzack "Shades" Highroost, who made a decent effort to recover Castle Calaelen, out of an adventuring spirit and a lack of anything better to do.
In 1790E, Shades would go missing, and the deed passed to his longtime friend Freydan De Jun. After Bent and Twiss asked very politely, Freydan passed the rights to Castle Calaelen on to the town of Dejune, and established a proper line of succession for the rights of the company. With this, after over 800 years, Bent and Twiss were free of one of the most annoying magical contracts in the Valley's history. The command of the company would pass to a Tsarthar named "Foil" Dragonfoil, who would spend the next 5 years struggling to fill the void left by the loss of Shades and the other Engineers.
Tragically, in 1791E, Bent and Swiss's offices would burn down. Although it was officially ruled arson, Molly was never caught. Bent disbanded the company, leaving Preston a free agent.
In 1795E, Shades would return, although Foil would remain the Head Engineer. The company would then partner with Mirrax Marines to create a new branch, named the Black Flag Company. Sponsored by Mirrax and staffed by GDEC, this company would lean on GDEC's roots as a survey/exploration company. We'll see how this turns out.