From Diablo Wiki

The Deckard Cain Rap is an easter egg created and published by the Blizzard Entertainment Company. The song consists of a very medieval-theme and of course, Deckard Cain bringing out his classical rap rhythm.





Performed by Deckard Cain's voice actor, Michael Gough, many lyrics from the song refer to dialogue in the game (but certainly not all, such as "Sean Connery" or "Patrick Stewart"). The rap consists of two-word, one rhyme rhythms. The melody is a simple jazz theme with a soft drum loop that quiets when Deckard Cain enters his verse. Here is the song (with lyrics) on youtube: https://www.youtube.com/watch?v=7HfmB4r2Fco