Pyro Abyss Mages are best countered with Cryo, Electro, or Hydro. Hydro is especially useful due to how the Vaporize reaction works. Cryo Abyss Mages are best countered with Pyro, Electro, or Hydro. Pyro is especially useful due to how the Melt reaction works. Hydro Abyss Mages are best countered with Pyro, Cryo, or Electro. Cryo is especially useful due to how the Frozen reaction works. Electro Abyss Mages are best countered with Pyro, Hydro, or Cryo. Pyro is especially useful due to how the Overloaded reaction works. If there are more than one Abyss Mage with different element types, then you can use Anemo to diffuse their elements together.
