This dragon uses very intense bursts of EM radiation as its “breath” attack. Obviously it can’t breathe light, but the attack originates from its mouth. This beam of light can permanently blind unshielded eyes and is hot enough to burn skin and ignite dry materials such as wood. In addition, the entire dragon is bioluminescent, and can blind attackers by raising its scales and releasing bright flashes of light. Finally, it is armed with a venom that reacts with the blood to produce a bright glow, allowing the dragon to track its prey in any weather or even total darkness.
The question here is: how could an organism generate and direct large amounts of electromagnetic radiation without using any type of technology?
Preferably, I would like the majority of the radiation to be between infrared and ultraviolet waves, but if other waves are easier to generate I’m ok with that too. I would like this answer to have as little handwavium as possible, and there is no magic in the setting. However, if this isn’t possible as far as our current understanding of biology and physics goes, then I’m willing to accept the most plausible sounding answer.