Attempting to tackle some of the abilities...
BOZ said:
Three great metal chimneys rear from its stern, spewing sparks and flames up to 30 feet into the air. (The fires cause any flammable material within 30 feet of the device to save vs. normal fire or burn.)
Combustion Cloud (Ex): Three great metal chimneys rear from the Apparatus's stern, spewing sparks and flames up to 30 feet into the air. Any creature or object within 30 feet must succeed on a DC X Reflex save or take an extra X points of fire damage as clothes ignite or armor becomes searing hot. The damage continues while within the area and for another X rounds thereafter. Unattended flammable materials within the area ignite automatically. The save DC is Constitution-based.
BOZ said:
Two monstrous studded wheels enable the apparatus to cross any terrain at a constant speed (MV 24,or 8,182 miles per hour), night or day.
That translates to a land speed of 60 feet.
BOZ said:
Most fearsome, however, are the eight human-sized metal teeth at its front, each driven by a great piston, which chew through every kind of stone, metal, or other substance. If the apparatus runs into a cliff or mountainside, it digs its way through at a reduced but still rapid speed (MV 18), leaving a permanent tunnel behind it. Any being run over by this device, whether crushed by a wheel or "bitten" by a metal tooth, takes 10d12 points of crushing damage and 6d6 points of heat damage (no saving throw), and must pass a system shock roll or die at once.
That translates to a burrow speed of 45 feet (or round down to 40).
Burn (Ex): The Apparatus's natural attacks deal normal damage plus fire damage because of the creature's great heat. Anyone hit by the Apparatus's natural attacks must succeed on a DC X Reflex save or catch on fire. The flame burns for X rounds. Unless it is still in contact with the Apparatus, a burning creature can take a move action to put out the flames. The save DC is Constitution-based.
Creatures hitting the Apparatus with natural weapons or unarmed attacks take fire damage as though hit by the Apparatus's attack, and also catch on fire unless they succeed on a DC X Reflex save.
BOZ said:
As the apparatus travels across the landscape, it destroys everything before it in a path 20 feet wide, moving in a perfectly straight (if not entirely level) line. Nothing, not even a wish spell, can turn it aside or direct its movements. Witnesses report that the apparatus is able to survive falls from considerable heights without damage, observing that it continued on its journey as if nothing happened. The single mindedness of the apparatus's movements and feats leads most observers to believe that it has escaped its original owner or creator and is now running without any intelligent control.
Immune to falling damage?
Immovable (Su?): The Apparatus cannot be moved by any means short of epic magic or direct divine intervention. It automatically succeeds on all opposed bull rush, grapple, and trip attempts.
BOZ said:
As it moves, part of the mechanism takes the rocky material it destroys, draws the debris into the vehicle, and leaves it behind in the form of a black paved road measuring 12 feet wide, with churned earth and ground rock littering either side. The created road is exceptionally durable, making all saving throws as metal +4. Immediately after the passage of the apparatus, however, the roadway is extremely hot, doing 6d6 points of damage to anyone who touches it; it cools by one die of damage for every hour that passes after it begins to cool. Furthermore, the road contains poisonous substances that kill all plant life within 50 yards for a full year. This road, though of high quality, of course leads nowhere in particular except by random chance. Any city unlucky enough to be in the path of the device must be abandoned until it has departed, leaving road and ruin behind it.
Road of Ruin (Su?): As it moves, the Apparatus converts destroyed material into a black paved road measuring X feet wide (I'd recommend the same as its Space), with churned earth and ground rock littering either side. The road has hardness X and X hit points per 5-foot section. The road is extremely hot, dealing 6d6 points of fire damage to anything that touches it within the first hour. For each hour thereafter, it cools, dealing 1d6 less damage until it is completely cool 7 hours later. Additionally, the toxic substances mixed with the raw materials are deadly to plants, automatically killing all plant life within 150 feet. Plant creatures are entitled to a DC X Fortitude save; even on a success, the creature still takes 5d6 points of damage. The save DC is ?-based.