Final answer:
The Janus Crest Mask from Ejagham, Nigeria, is made of antelope skin with a glossy finish created by the application of palm oil.
Step-by-step explanation:
The Janus Crest Mask from Ejagham, Nigeria, which was created in the 20th Century, is composed of antelope skin as the primary material. The glossy finish on such masks is traditionally achieved using palm oil, which is applied to the surface of the mask. The application of palm oil not only provides an aesthetic sheen but also acts as a preservative for the organic material of the mask. In this case, the correct answer to the question regarding the material and substance used for the glossy finish of the Janus Crest Mask would be antelope skin and palm oil.