Although no exact date is known, the Mark XXXIV was introduced sometime between 3311 and 3408. The Mark XXXIV mounted two Hellbores, an unspecified number of mortars, and two Hellrails. The Hellrail was a 60m long railgun with a yield of 90 megatons per bolt, with a reloading period of 1 to 1.2 minutes. The Mark XXXIV was designed to provide orbital cover for Bolo brigades as they were able to engage ships before they entered orbit. Nothing is known about the weight of the Mark XXXIV, but it had a combat sprint speed of at least 200km/h.
The design of the Mark XXXIV - and all known units - was lost following the end of the Melconian Holocaust.