Sardak

The are NaN Sub-Bosss in.

They serve ZA:, and are invulnerable to every weapon except for the ZA:. ZA: must defeat every one of them to remove the ZA: in front of ZA:'s room. They come in three colors: Blue, Red and Yellow, with Blue being the weakest (taking 2 hits to defeat) and Red and Yellow being the strongest (taking 4 hits each to defeat).