From Destinypedia, the Destiny wiki
A Taken Forerunner is a powerful enemy that appears during the Getting Your Hands Dirty Adventure in the EDZ. It appears as a stronger version of major Taken enemies such as Captains, Phalanxes, Minotaurs or Centurions. Its death spawns a Taken Blight which summons five Taken Psions that the player needs to melee kill in order to progress.
List of appearances