I've been buying up out of print Tekumel material to help me build more depth into my current game. I've got the old Seal of the imperium volumes 1 & 2 (published by Carl Brodt) on order and he's trying to find copies of the old Sword and Glory Tekumel maps for me as well. I've got a copy of the old Tekumel Bestiary on order from Noble Knight Games as well as the old Players Guide to Adventures on Tekumel from TOME. I'm looking for cheapish copies of Gardasyal's three volumes from 1994 as well to complete my collection.
A random retweet that grabbed some of my feedspace, took me to The Keys of the Kingdom on Drivethru, a nice self contained kingdom in peril with a showcase of Chris Walton's art, a map, and a shell of a campaign outline. Great to use this and plonk into a game world map and just go with the stories there.
Although there is a skeletal OSR game within, you'd just pick your fantasy game of choice. It's bare bones, so it is down to you to put some meat around it and that could be done collaboratively at the table. Pathfinder 2e and Omni are calling to me.
That looks funky. I shall wishlist it. Link here if anyone else interested.
A nice little sandbox is often great fun. Similar to Dolmenwood that Tom likes. I had a similar play with Questers years ago using Fish Side by The Forge (the art people not the forum) - a town with artwork and adventure seeds (I'm guessing you could slot it in to one of the above).