On Mobile, the TEMPLE OF SET medallion is between Sewers of Severance and Burrows of Beholder.
If you play on Mobile, and don't have a Set medallion there, contact Pixel Support.
From your game screen, choose the Settings cog (upper left corner). Make a note of your Player ID. Then choose the Support button. Choose a category from the bottom half of the screen.
Don't enter something in the text box at the top of the screen. That just sends your entry right back here to the player forum.