He was tricked by Cartaphilus to kill cats to create a potion to strengthen his wife's body. Instead, she melts. He becomes mad and believes he can still cure her and walks about of their home with the intent of killing more cats. The First Cat King stops him and he and the remaining cats devour Matthew. He becomes part of the stagnation by the lake.
Skills and Abilities
↑Mahou Tsukai no Tsukai Manga — Vol. 2 Chapter 6,
Matthew refers Mina has his wife.