Plasmodium reactor - Cost: Water + Portable fusion reactor x10 = Plasmodium Reactor. (And Oxygen, since only the Hydrogen is used, but throw that into the air!) Or, Natural Gas (Basically, oil.) + Portable Fusion Reactor x2 = Plasmodium Reactor. Plasmodium - Basically plasma. The plasma can be used for all sorts of things - Furnaces, for example. Also, it is several thousand degrees celsius in heat, so it would go super fast. Compare that to the center of the earth, which is only about six thousand degrees celsius. Plasma guns could be pretty fun too.
For some non-real items...
Alienios. (Pronounce "Alien" then pronounce "EE-os") Made from lots and lots of alien artifacts, however, a very strong structure. The walls are so strong they're fully fireproof.
Energium. (Pronounce Eh-Ner-gee-um) Using very tiny and portable fusion reactors, energium heals itself. 1 portable fusion reactor makes 100 units of the stuff. Due to regenerative properties, it takes no damage from acid, but double damage from physical attacks (such as the biter's melee) due to directly damaging the generator.
Graphene. A real substance! Made from Graphite, a crystalline structure of Carbon, found in Coal. Sticking tape to graphite and removing it IRL gets a one-atom-thick layer of graphene. Strongest material known to man Can carry 200x as strong as steel!!!! Takes no damage from physical attacks, but 50% more damage from acid, due to melting it away.
Plastic wall- Low health, no resistances except laser. Takes no laser damage (due to not conducting electricity, and actually not doing anything to it.)
1 plastic wall + 5 graphene walls + 5 energium walls + 1 Alienios wall = 1 Unbreakable wall. No damage from lasers, physical (biters) acid (spitters) or fire (flamethrowers.)
EDIT: You can use these (as long as you put somewhere that they were my idea!)
EDIT2: forgot the ) in EDIT1
