The Jade Temple in Secrets of the Sokol Keep in AL season 1 (DDEX 1-2)

• It has a spiral shape
• There is a magical jade idol that (supposedly) depicts Dagon in the center.

The Jade Temple in Secrets of the Sokol Keep in AL season 1 (DDEX 1-2)

You can find "Secrets of Sokol Keep" here on DMsGuild. Part 3: The Jade Temple (starting on p. 17) describes the dungeon you're thinking of:

• It has a spiral shape
• Area 6 contains a magical jade idol that (supposedly) depicts Dagon in the center.