tf? this is the worst review ever seen by mankind. You were supposed to give us a professional and detailed explanation of what the mastery does and how it affects the tower on each level, not a colloquialist video "Oooh naaao this sucks :
Fun fact: if Doombringer spawns, any Boombox with max mastery says "Raghhh that is it!!! I'm going beast mode!!!" And will deal .25 extra damage however it gets rounded down to the base lighting damage