The spelling of the word "doest death" may seem confusing, but it is a archaic form of the phrase "does death" which means 'will die'. In IPA, it would be transcribed as /dʌst dɛθ/. The word "doest" is an outdated form of the verb "does" used in the second person singular. So "doest death" could be understood to mean "you will die". As with many archaic forms of English, it is rarely used in modern speech or writing.