Mateusz Śmierzchalski
 Mateusz Maurycy Śmierzchalski (born 18 July 1982 Gdynia Poland) stage name Havoc is a Polish heavy metal musician. He is best known for being the rhythm guitarist lead guitarist and backing vocalist for Behemoth. Since 1999 he is leading guitarist of the sludge-doom metal band Blindead.Mateusz Śmierzchalski is endorsed by Mayones.