A heavily modified version of the original AD&D. I called it “Servant” because a major theme of the system was that no matter how high you rise, you’re still serving somebody, the only question is do you pick whom you’re going to serve or are they picking you?
And to emphasize the point, there was a mad wizard in a tower whose bottom eight or so floors (and four basement levels) were firmly on the ground, and whose top half-dozen floors were visible more or less above those, up in the sky, while the three dozen or so floors in between were sort of shifted into another dimension (and tended to be larger on the inside than the ostensible diameter on the outside) – and this guy had servants who were L19 or L20 mages themselves, along with guards among whom the equivalent of a PFC was an eighth or ninth level fighter type.
One of the secrets of the game world was how big it was; the surface area was something like thirty-two times the Earth’s surface area yet had a gravity that gave a nice round 10 meters per second squared on the surface. One of my groups of players got creative and decided to sail off to find a rumored/legendary next continent to the east, and they took a trio of sages along to see what they could learn. When they made landfall after crossing about 120% of the distance across the Atlantic ocean – after sailing about the length of the coast of South America before leaving their home continent – the sages set up some instruments and by noting the times at which the three moons rose determined how far they’d come and the circumference of the planet. When they announced their results, a bit of meta-gaming ensued; one of the players started uttering under his breath while staring across the room and after a minute – during which we all remained silent – he looked at me and said, “The damned thing’s hollow!”
They had along a device that let one person only portal back home (a device that had to be renewed at a cost of some 100k gold), and they were on a friendly basis with one of the mad wizard’s aides, plus they figured if anyone knew the truth he would, so they sent their cleric back (the one character class the wizard had any respect for) to ask if the sages were right, and having caught the aide in a good mood the cleric learned that the world was constructed thousands of years earlier by the wizard’s father, and the family had been exiled from the inside… at which point the aide caught himself and shut up, mumbling, “You didn’t hear that from me!”
I actually worked out how thick the shell had to be assuming a surface structure similar to that of Earth, then the strength of that shell and found what I expected: it wasn’t strong enough by itself to hold together – so of course it was held together by a magical substance which exerted its own force of gravity for the inner surface without bothering the outside. One nice thing was that the shell was thick enough to allow for plate tectonics… so I bought one of those colored basketball-sized balls at a store, a pale blue one, and proceeded to transfer what I’d already mapped of the original continent and the new one, and added ten more for good measure, and marked off the plate boundaries in a shade of orange that contrasted joltingly with the pale blue of the ball. One of the players in another group was a geology major, so I roped him into helping figure out where various mineral deposits could be – he pointed out that the surface was probably accreted from bodies it ran into in space and so I could really put any minerals I wanted anywhere at all!
Somewhere in storage I still have all the files from over a century of game time including copies of the character sheets of every player in my various groups plus notes on every political system I worked up for the two continents down to royal family lineages… I sometimes think maybe I should find someone who would put it to good use given that I’m probably never going to run it again.