Shell medium-sized for the genus (up to 27.6 mm in length), thin, claviform to fusiform with high spire, about 10 teleoconch whorls, suture shallow, whorls shouldered. Subsutural cord strong, slightly undulating in apical view, slightly bifurcated. Subsutural slope slightly concave and about two times wider than subsutural cord with thickened scars of anal sinus. Aperture narrow with a long, curved, and slightly notched siphonal canal. Labial callus forming a fairly thick tongue-shaped nodule in posterior angle of aperture, slightly intruding into opening of anal sinus and constricting it. Columellar callus thin, smooth and indistinct, free outer edge on the anterior part. Outer lip thin, with a very shallow stromboid notch. Anal sinus deep, openly U-shaped, slightly adapically directed. Sculptured of strong rounded axial ribs, abruptly ending on shoulder, extending well onto rostrum. Axial ribs more or less equal to their intervals, about 9 axials on first teleoconch whorl and about 12 on penultimate whorl, including 1 or 2 varices per whorl. Dorsum of body whorl with a rounded varix, situated about half whorl back from lip. Primary spiral cords very faint on early whorls, about 5 spiral cords on later teleoconch whorls, interspaces about 2 times wider with additional faint secondary spiral threads, about 6 or 7 faint and densely-set spiral threads on the shoulder slope. Protoconch bluntly conical in shape, consisting of about 2,5 smooth whorls, first whorl depressed, followed by weakly convex whorls, suture shallow, glossy, transition to teleoconch ill-defined.
Background colour white to cream with irregularly shaped pale to golden brown areas mainly in the interspaces of axial ribs; varices white, axial ribs white or light brown (in general paler than interspaces) just behind the varices. Subsutural cord with irregular-set light brown dots. Base of last whorl with irregularly shaped light to dark brown spiral bands. Protoconch white.


No soft parts or operculum are available for study.

Inquistor modulatus sp. nov. is rather similar to Inquisitor ritae Stahlschmidt & Fraussen, 2017 [type locality: Philippines; Aliguay Island, 50-150 m], but differs in the more shouldered whorls (resulting in a pronounced shoulder slope), the thinner and slender shell, the longer siphonal canal, and the darker shell colouration.
Etymology: Inquistor modulatus sp. nov. is derived from the Latin adjective modulatus, meaning "in the cadence" or "harmonious", which refers to the axial ribs that are nicely regularly spaced.

Type locality: Philippines, Mactan Island, off Punta Engano, 100-250 m. Type material: Holotype: MNHN-IM-2000-37765, 27.6 mm, Philippines, Mactan Island, off Punta Engano, 100-250 m (trawled). Paratypes 1-3: PS-976, 25.0 mm, 25.5 mm, 23.7 mm, type locality; Paratype 4: KF, 22.5 mm, type locality; Paratypes 5-6: MSF, 24.2 mm, 23.5 mm, type locality; Paratype 7: MNHN-IM-2000-37766,
22.5 mm, type locality; Paratype 8: PS-977, 22.7 mm, Philippines, Mindanao, Aliguay Island, 50-150 m; Para¬types 9-10: MSF, 27.1 mm, 22.5 mm, same locality as Paratype 8; Paratype 11-12: MHNG-MOLL-0138923,
25.5 mm, 30.2 mm, type locality. Distribution: So far known only from the central Philippines (Mactan Island and Aliguay Island).