From Introduction: The d20 Future Mecha rules offer a good basis for detailing humongous walking machines of war, but there are areas where it could be further expanded. One such area has to do with what makes mecha go, the source of their power. Nothing is said in d20 Future about a mecha’s power source, so all we can assume is that a mecha has one, it never runs out, and has no other effect on a mecha except to “make it go.” Obviously, there is a level of detain here that needs fleshing out. These optional rules are hereby presented to add that extra layer of detail to your d20 Future mecha.