Mount Doom

The Mountain crept up ever nearer, until, if they lifted their heavy heads, it filled all their sight, looming vast before them: a huge mass of ash and slag and burned stone, out of which a sheer-sided cone was raised into the clouds.

Normal sudoku rules apply.

The diamonds indicate where Frodo, Sam, and Gollum are on the mountainside. Fill these cells with the digits that were discovered in the Elven boats in 'The Great River'.

Along SLOW thermometers digits stay the same or increase as they move away from the bulb.

Lava flows (orange lines) are palindromes and read the same in both directions.

Red fireballs (dots) separate two digits where one is double the other. Yellow fireballs separate consecutive digits.