What is correct meaning for munchkin: a child or short person or a player who plays in an aggressively competitive manner? This is important for correct translation to Russian 
‘Munchkin’ isn’t translated usually in Bulgarian: "Светът на мънчкините винаги е бил пародия предимно на фентъзи световете и персонажите. " But the noun exists in the dictionary: “munchkin [´mʌntʃkin]
n ам. разг. дребосъче, фъстъче, дребно сладурче, мъниче.”
I’m 100% sure you don’t need translation from Bulgarian 
I think ‘munchkin’ cannot be translated properly in any language and must stay unchanged ‘мънчкин’
Oh yeah, that game is so fun btw.
In some languages, we do the equivalent of “small monster”, but I think transliterations of “munchkin” are perhaps most appropriate.