I'm running a 5e Eberron campaign. My players are about to discover that Lhesh Haruuc is secretly building a lightning rail line from Rhukaan Draal towards Sterngate, aided by a rogue scion of House Orien. In this campaign, slavery is legal in all of Darguun (contra the statement on pg. 112 of the official 5e campaign setting). As a result, other nations and dragonmarked houses are extremely reluctant to deal with Darguun: think anti-apartheid divestment. So Haruuc is funding this project himself, with assistance from his collaborator from House Orien and his own slave labor.
I want to determine, realistically, how quickly this line could be built. Haruuc thinks greed will take over once he connects to existing rail lines, and that House Orien will start sending trains to Darguun. So he isn't building trains; he's only identifying the best route, grading it, and installing conductor stones. The big unknown here is the conductor stones:
- How much does the raw material for a conductor stone cost?
- What level of magical ability is needed to manufacture a conductor stone, and how long does the process take?
A conductor stone is clearly a magic item of some kind, but it's not clear to me what its rarity is. This post indicates that in some previous edition the conductor stone was described as an air elemental bound in a Khyber dragonshard; however, I can't find any explicit statement to this effect in the 5e book. Pg. 235 describes the conductor stones but implies that they're distinct from whatever holds the bound elemental:
Each cart...has a conductor stone embedded in its underside. A corresponding set of conductor stones laid out in a line on the ground interacts with the stones in the carts to form a rail for the train to follow. Lightning arcs between the two sets of stones, accounting for the system's name.
The elemental vessel at the front of the train, called a crew cart, holds a bound air elemental that propels the train along its route...
Similarly pg. 275 states that air elementals bound in Khyber dragonshards are the basis for the lightning rail, but doesn't mention conductor stones.
This old post asks about the price of conductor stones, but it seems to be asking about finished stones, not the raw materials or the labor required. (And the discussion didn't reach a conclusion anyway.)
I'm not interested the mechanics of the actual procedure for creating a conductor stone; my characters probably won't be doing this. (If they do, I can use the suggestions in these answers for inspiration.) Rather, I want to get a sense of how the process scales up. I'm happy to assume that Haruuc has enslaved high-level magic users (including gnomes, if necessary for elemental binding) and/or skilled artisans from House Cannith. If I can get a sense of how much gold the raw materials for one conductor stone would cost, and how many person-hours are required to create one, I can extrapolate costs per mile of the lighting rail line.