"C" is for "Crocroach"

Crocroach

No. Enc.:  4d6 (6d10)
Alignment:  Neutral
Movement:  135' (45')
         —Fly:  45' (15')
     —Swim:  90' (30')
Armor Class:  3
Hit Dice:  4 hp
Attacks:  1 (bite)
Damage:  1d3
Save:  L3
Morale:  11
Hoard Class:  VI
XP:  9

Vicious little beasts, crocroaches are foot-long monstrosities that infest all places damp, dark, and dire—cesspits, caverns and mines, toxic dumps, Ancient ruins, and the like.  They possess 3 black, bulging, compound eyes (meaning they are never Surprised), thick hides, and rows of needle-like teeth.  Crocroaches skitter up vertical surfaces, and across ceilings, with ease.

A swarm always signals an impending attack by hissing at potential prey for 1d3 rounds...and then the mass surges in a frenzy of chitin, scales, and fangs.  Each crocroach latches on with a successful bite, and does automatic damage every round.  They can skeletonize a full-grown humanoid in under a minute.

And if you think the small ones are bad....

Mutations:  Accumulated Resistance (Pollutants), Increased Sense (Smell), Night Vision

Crocroach, Giant Albino

No. Enc.:  1 (1)
Alignment:  Neutral
Movement:  150' (50')
         —Fly:  75' (25')
     —Swim: 105' (35')
Armor Class:  0
Hit Dice:  15
Attacks:  1 (bite or tail-slap)
Damage:  3d10 or 3d6
Save:  L10
Morale:  11
Hoard Class:  XXII
XP:  6,900

Denizens of the Mutant Future tell tales of the horrors that dwell in the sewagey bowels of ruined cities...and none is more horrible than the giant albino crocroach.

Over 50' long, giant albino crocroaches are the undisputed apex predators of their underground kingdoms.  The Swallow their prey on natural To Hit rolls of 16-20, and those thus consumed suffer 2d6 damage per round until perishing (or cutting their way free).

There is a 45% chance that any given giant albino crocroach will have either the Toxic Weapon (usually a breath attack) or Energy Ray (that does an additional +2d6 damage) Physical Mutation.  [Adjust the XP value accordingly.]

Mutations:  Accumulated Resistance (Pollutants), Albinism [D], Increased Sense (Smell), Night Vision, Reflective Epidermis (Radiation), Vision Impairment [D]