The original Guardian case was one of NZXT's first chassis. Released in 2004, it had a robot-themed design with side panel window, LED lighting, 80mm fans and was available with an optional 400w power supply. Although the Guardian 921 is also a steel mid-tower chassis with a side panel window, LED lighting and optional 400w power supply, I don't see much resemblance between it and the original, and am a little confused as to why it didn't get its own moniker or what significance the number 921 holds.
The original Guardian was available in black, silver, blue, gold, green or orange, and had red and chrome trim in addition to blue LED lighting, quite the myriad of colors there. In contrast, the Guardian 921 is available in black only, and similar to other cases in the Crafted series, like the Apollo or Zero, has a much more subdued appearance than the wild designs of the original Guardian or Nemesis. The packaging is typical for many cases and prevents most forms of damage during shipping.
The Guardian 921 is advertised as having nine drive bays, which is right on par with most mid-tower designs, but that number might be slightly optimistic. The rest of the specs are fairly typical of other cases this size. The Guardian 921 comes with three 120mm fans, two of which are LED, so the end user doesn't have to worry about providing fans of their own to fill empty spots in the case.
Let's take a closer look at the NZXT Guardian 921.