Solo This!! Fantasy
Compatible with Survive This!! Fantasy
The Survive This!! family of games blends the basic gameplay of OSR with a simple-to-grasp skills system. The Fantasy version of this game is well supported by Bloat Games with many companion books. This is a buy as much or as little as you need to play your game.
The stand out feature, for me, is the magic system with its inherent risks when stepping into the void.
My only disappointment was the lack of monsters in the core book. That said, it is the work of a moment to convert any OSR monster book to ST!!Fantasy.
These rules have a definite OSR feel about them, but are designed to dovetail into the Survive This!! rules as written.