Oh, there are so many... Yeah, it's a rabbit hole.
For now, check out:
https://huggingface.co/LatitudeGames/Harbinger-24B (and literally anything from Latitude Games, who explicitly specialize in dungeon master models for their site).
https://huggingface.co/PocketDoc/Dans-DangerousWinds-V1.1.1-24b
https://huggingface.co/Gryphe/Codex-24B-Small-3.2
24Bs are very tight on your card (but so smart they're worth it), so you will want ~3.6bpw (10 GB-ish) exl3 quantizations to minimize the quantization loss and keep them fast. They're easy to make yourself if you know a little command line and have decent internet; I can walk you through it.
Or I can just quantize these three models just for you, overnight, if you wish. Maybe check how much VRAM your desktop takes up at idle so I can size them right, and let me know.