Graymalkin's mutant powers are related to light exposure; the darker it is, the greater his powers become, the absence of light triggering his powers.His powers strengthen with a lack of light, and he is weaker with exposure to light. Doctor McCoy stated he was unpowered in presence of light. Graymalkin has demonstrated the following powers:

Superhuman strength, or enhanced, to an unknown degree

Longevity (or possible Immortality) allowing him to survive without food nor water indefinitely: In complete darkness, he was able to survive 200 years with neither food nor water.

Night vision allowing him to see clearly in total darkness