Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
‡ necrŏmantĭi, ōrum, m. [necromantia], necromancers: necromantii sunt, quorum praecantationibus videntur resuscitati mortui divinare et ad interrogata respondere, Isid. Orig. 8, 9, 11 (al. necromantici).