|"House of Cards" by Indenture is licensed under CC BY-ND 2.0|
About 2 months ago I started a new campaign. I was ambitious, I created a fairly open called Ær. The concept was that the player characters are agents of a kingdom built on a chain of floating islands. I borrowed much of the geography and basic concepts from the kingdom of Floating Ar in Mystara after the cataclysm in the Wrath of the Immortals and then mutated it until it was functionally unrecognizable.
The players are a group of young people who have won a lottery and been given a chance to psychically bond with wyvern (think Dragon Riders of Pern). Those that make the bond become members of a knightly order dedicated to furthering the kingdom's needs. They fight the terrible floating pterosaurs that prey on the region, explore a mainland overrun by lovecraftian horrors, chart the islands that their homeland passes over, and run diplomatic envoys to known kingdoms that were not overrun by the eldritch things.
While I started the campaign using index card RPG for 2E, I was inspired by Stephen Smith to build a custom B/X game for it. This included creating a class of ace dragon riders as an option, replacing clerics with alchemists that were talented surgeons, and importing the pact magic system from Lucas Rolim's Pacts and Blades: Moorcockian Fantasy RPG to give me a magic system consistent with the idea of someone who forms psychic bonds. Clerics exotic and foreign type of magician unavailable for play, and Magic-Users as members of the ruling elite were not permitted to bond with Wyverns (That's work for people who are expendable.)