Fiendfyre
Fiendfyre is a powerful and magical fire in the Harry Potter series, known for its ability to consume anything in its path. Unlike regular fire, it is difficult to control and can take on a life of its own. It is often depicted as a greenish flame that can burn through magical protections and even destroy Horcruxes.
This dangerous fire is conjured using advanced dark magic, making it a tool primarily associated with dark wizards. Due to its uncontrollable nature, it poses a significant threat to both the caster and their surroundings, leading to its classification as a forbidden spell.