Nepenthes diabolica is a tropical pitcher plant known only from a single mountain in Central Sulawesi, where it occurs at c. 2200–2300 m above sea level.

[5] It is characterised by an exceptionally developed peristome and conspicuous, woolly pitcher indumentum.

Morphologically it is closest to N. hamata, the only other species from Sulawesi with a similarly elaborated peristome.

[5] The species was known to botanists as early as 2005, when Ch'ien Lee announced the discovery of a new form of N. hamata with an exceptionally dense indumentum.

[7][5] The specific epithet diabolica is Latin for "diabolical" or "devilish" and refers to both the typical red colouration of the lower pitchers and their greatly enlarged peristome teeth.