The shell shape and sculpture are constant in the three analysed specimens. The species exhibits a conical morphology, dorsally raised, with a very thick and non-translucent shell . The anterior part of the animal is laterally compressed. The shell is of medium size (maximum length 80 mm) and exhibits a high profile. The apex is situated at the anterior 40% of the shell. All the slopes are convex. The aperture is oval. The surface of the shell is sculptured with raised angular primary radial ribs, weaker secondary ones and concentric growth lines that are visible in the interspaces. The margin of the shell is crenulated. The external coloration is pale reddish-brown and grey. The primary and secondary ribs are red-brown to ash-coloured to dark brown with clearer interspaces. The internal part of the shell has a soft metallic-brown coloration with dark lines corresponding to external colour patterns, bordered by a white/brown halo. External anatomy: The ventral area of the foot is grey and the epipodial fringe is quite recognizable. The mantle fold is thin and dun-brown coloured. The mantle tentacles are not pigmented and in alternate series of three white and a white longer one. The cephalic tentacles are dorsally pigmented with a black line. Radula: The first lateral teeth are set close together on the anterior edge of the basal plates, long and sharp pointed, with two long cusps. The second laterals are broader, wider spaced with three short cusps.

Campbell Island, sub-Antarctic New Zealand.
Habitat: Low intertidal and subtidal rocky ecosystem down to 30 m.

Multilocus phylogenetic reconstructions recognized N. terroris from Campbell Island as a distinct taxonomic unit, closely related to Macquarie Island's N. macquariensis and to N. edgari from Kerguelen and Heard Islands. Phylogenetic relationships and divergence time estimates indicate that Nacella species from New Zealand (N. terroris) and Australia (N. macquariensis) constitute a recent offshoot from the Kerguelen Archipelago (Gonzalez-Wevar et all.,2017).