Ultimate Fire Demon

This demon only appeared in the episode "Forces of Nature." Here, Slade tricks Thunder and Lightning into using their powers to explode a bunch of seemingly randomly placed scarecrows, seemingly for their own amusement. When they have completed the task, they realized they were used. The scarecrows were arranged in a Mark of Scath and this gave birth to the demon, showing it is clearly spawned from Trigon. It is a gigantic monster which has a thick, flaming aura and great pyrokinetic powers, as well as that it has powerful direct damage properties. Beneath the flaming aura, it appears to look somewhat like a black skeleton. It was so powerful that the Teen Titans alone could not stop it. Thunder and Lightning corrected their mistake and destroyed it with thunderstorm-level rain.

Trivia

 * This demon appears to be a gigantic version of one of Trigon's fire demon servants.
 * Although the power of the 5 Titans could not stop it, interestingly, a rather simple part of normal nature (rain) could.
 * Here, Slade also wore a medallion with the Mark of Scath on it. At the end of the battle, he disappeared, leaving only the medallion behind. Interestingly, when Robin saw it, the 'S' let him to believe that the villain was Slade, which was indeed true, but Robin's reason was, in fact, incorrect, as the 'S' stood for 'Scath,' not 'Slade.' This implies either that he was associated with Trigon all along, hence why he was chosen as his herald after death, or that he simply has knowledge over the occult and is merely a coincidence.