The Grand Contrivance

"Long ago, for all such tales begin this way if they are to be of any value at all, a group of mages faced a dark threat. The specter of slow doom hung over the world, its tendrils spreading from land to land. The elements themselves were turning upon the people, vast storms wiping away coastal cities, unending droughts plague the plains. All was thought to be lost.

But they would not have it, these mages. They rallied the people, from each continent they came, flotillas of carpenters, masons, engineers and laborers. For you see, the mages had an audacious plan."

"What's odd-ay-see-us mean Papa?" Tavertine interrupts. He smiles and boops the girl's nose. "It means bold or risky young one" he explains, then licks his lips and turns back to the book.

"The mages plied their magicks, using the various druid Conclaves to dig deep, deep into the earth itself.  Once far below, where the rock is molten and runs like water, they carved vast tunnels. The design was unknowable save to the mages who were overseeing the project, yet the workers placed blind faith in this, their only hope. It took years for the construction to finish, and when they were done the entrances were capped and sealed, so that none could interfere with the grand design. Indeed, their efforts bore fruit, for the world settled down. To many, this may seem a tale of magick overcoming the odds, a tale of man overcoming the elements, but those people are fools. This is a tale of the many coming together to work for a common goal. No wars were waged for a long while after that, while those who remembered the upheaval still lived. You see, no matter how dark it may seem, no matter what the tragedy unfolding, you will always find those willing to rush in headlong to lend a helping hand. So long as that holds true, there will always be hope."

Entrance
The door to the capstone building requires an offering of power. A crystal in the center can be powered by pouring spell slots into it. 5 are required to open the door. Inside the room is simple, featuring a hole about 50 feet wide. Looking down the hole, the sides disappear into darkness, ending in a very soft orange glow. The sides of the tunnel down has a very thing, maybe 2.5' carved stone stair jutting out from it. The stair is just slabs of rock jutting out, less a built structure. The tunnel goes down for miles, taking hours to traverse, before opening into a vast cavern about 800 feet tall. The problem is that the stairs have eroded over time, there are three sections missing. The first two can be crosses either by climbing the rough wall (Athletics DC16) or jumping to the next stair, a gap of about 15 feet (Acrobatics DC16). The last is more problematic, there's a gap in the stairs about 50 feet vertically, the entire section missing.