"Martin Delrio" is a pen name used by Debra Doyle and her husband James D. Macdonald for their collaboratively written fiction. Numerous books from several fictional settings including Spiderman and Mortal Kombat are credited to the name (sometimes as co-writer).
For BattleTech, three novels in the MechWarrior: Dark Age series are credited to Martin Delrio: A Silence in the Heavens, Truth and Shadows and Service for the Dead, collectively also known as the "Proving Grounds Trilogy".
The pseudonym may have been inspired by the real, historical Martin Delrio, a Jesuit theologian, scholar and professor. Of the many books he wrote, one, written in 1599/1600 as a guide for inquisitors and judges, deals with witchcraft and the occult. It was reprinted many times over the following 150 years and Delrio is accused of having contributed greatly to witch hunts through it, and having been the principal cause for contemporary witch hunts in the southern Netherlands in particular.