"C" is for "Crotaloid"

Crotaloid  ("Rattleman")

No. Enc.:  1d3 (1d6)
Alignment:  Any
Movement:  120' (40')
Armor Class:  5
Hit Dice:  8
Attacks:  2 or 1 (2 bites, or 2 claws, or 1 weapon)
Damage:  1d8 + poison / 1d8 + poison, or 1d6 / 1d6, or by weapon
Save:  L8
Morale:  9
Hoard Class:  XIX
XP:  6,020

Crotaloids are gregarious serpent-men that always have an angle, and they're so slick they could sell a broken lightbulb to a luminoid.

Crotaloid eyes crackle with cobalt radioactivity [Class determined at random], and each head can target separate foes (essentially doubling the standard use of the Energy Ray mutation).  And their bites are venomous [Class also random].

Before teleporting, crotaloids rattle their tails at freakish speeds.  It is hypothesized that mimicking this frequency via technology could unlock newfound ways of traversing the cosmos!

Mutations:  Dual Cerebellum, Dual-Headed, Energy Ray (Radiation) (x2), Intellectual Affinity (Bartering), Plane Shift, Teleport, Toxic Weapon (Venom) (x2)

"S" is for "Splicesaur — Spinetitan"

Splicesaur — Spinetitan

No. Enc.:  0 (1)
Alignment:  Chaotic
Movement:  150 (50')
Armor Class:  1
Hit Dice:  26
Attacks:  3 or 1 (2 claws, 1 bite, or 1 tail, or 1 stomp)
Damage:  2d8 / 2d8 / 5d12, or 3d10, or 5d8
Save:  L13
Morale:  11
Hoard Class:  XXII x2
XP:  39,500

Spinetitans are four-eyed, building-sized (30'-40' tall) horrors that terrify the mightiest beasts of the Mutant Future; even the monstrous trirannosaurs give them a wide berth.

In addition to their crushing jaws, jabbing thumb-claws, and spiked tails, spinetitans discharge bolts of electricity from their cranial horns that inflict 8d6 damage.  Furthermore, any and all individuals wearing metal armor within 30' of a struck target suffer 4d6 arcing damage.

Spinetitans perceive not only the full electromagnetic spectrum, but also the ordinarily invisible energies surrounding those with Mental Mutations.  Consequently, the creatures always target psionicists first.

Spinetitans freakishly vocalize via clicks, whirrs, and chirps.

Mutations:  Echolocation, Enhanced Vision (Night, Thermal, Ultraviolet), Neural Telekinesis, Pain Insensitivity [D], Unique Sense ("Mento-Vision", X-Ray Vision)