There are at least 3 bands named "Kat":
Polish heavy / thrash metal band (with very few black metal elements) accused of propagating satanism. Considered as one of bands having most influence on Polish metal music.
The band was founded in the end of 1979 by Piotr Luczyk (guitars) and Ireneusz Loth (percussion) in Katowice. Soon next two members - Tomasz Jaguś (bass) and Ryszard Pisarski (guitar) - have joined the band. Kat was playing instrumental hard rock then.