In an alternate universe similar to the Coreverse, Deathwing ursurped the powers of Nozdormu to reshape time to his liking. After he hade done this, the very timeline of the universe changed, and not to the better, for most people. The term "Tyrantverse" is not used by the general inhabitants of it, but rather by dimensional scholars. It is believed that the term refers to the Three Great Tyrants: Deathwing, Thoradin, and Hellscream. This universe is indeed one much more grim than most others.