Overheat is one of the most powerful fire-type moves that you can find. This move has a power of 130 and an accuracy of 90. When it hits, it deals a lot of damage. It’s only fitting that this move would be hidden late in the game. Here is where you can find TM50 Overheat in Pokémon Brilliant Diamond and Shining Pearl.
To find this TM, you will first need to reach Stark Mountain. To reach Stark Mountain, you will need to defeat the Elite Four and obtain the National Pokédex. Once that is done, head over to Snowpoint City and take the boat over to the Fight Area. You find Stark Mountain by traveling north on Route 225 and going to the east when you reach the Survival Area.
Enter Stark Mountain and progress until you reach the room where you meet up with Buck. If you have already been here before, go to the second room of the mountain. After traveling down the long, thin platform, head left and go down the stairs. Keep traveling north until you are stopped by a wall. Take the path to the left and move the boulder out of the way. Head south and defeat the pair of Elite Trainers. On the other side of the trainers is where you will find the item ball containing the TM.