While the marriage of Iravan's parents is mentioned in the first book of the Mahabharata, Adi Parva (the Book of Beginnings), both the birth and death of Iravan are mentioned later, in the sixth book, Bhishma Parva (the Book of Bhishma) [REF].
Agitated by this reversal, the eldest Kaurava, Duryodhana, orders the rakshasa (giant) Alamvusha (or Alambusha), son of Rishyasringa, to kill Iravan.