Melchor is a middle aged man with emerald eyes.
When he uses Pan-Rozum, his body changes into a flying blob of mercury without any recognizably human characteristics.
Melchor is generally very serious and humorless. He is also supportive and nonjudgemental towards his loved ones, and has the same stubborn sense of honor as most Rainlords.
Following a string of deaths in the Blackburn family, Melchor left to work through his grief alone. He returned shortly after the Elroy Massacre, and greatly surprised Ismael by not only forgiving him for his actions but supporting him in his decision to protect Ibai rather than tell the truth to the Vanguard or the other Rainlords. Before the battle against the other Rainlords, Ismael had Melchor swear that no matter what, he would kill Parson and have vengeance for his family.
When the other Houses attacked, Melchor was forced to fight against Xuan Sebolt, and defeated him. However, Hector and Asad were able to rescue him and protect his reforming body until he could return to Pan-Rozum and defeat Melchor.
Normally, Melchor's power is fairly limited. The only application of normal transfiguration that Melchor is shown using is explosive mercury fulminate. However, he becomes far more dangerous when he uses Pan-Rozum. He can transform his entire body into mercury and use both liquid and frozen mercury at high velocity and backed with soul power to perform a variety of attacks. Not only does Pan-Rozum grant Melchor incredible mobility and the ability to use Materialization, it also makes his body nearly indestructible.