Nilhogg's nose was a small fungus that grew in the Deepways, thought to be shaped like a Human nose with a mustache underneath. It was edible, but provided no nutrition.
When consumed, it enhanced the sense of smell of the consumer for one to four hours, improving the chance of detecting and identifying odors. However, under the influence of this mushroom, the consumer was also more vulnerable to the effects of smells, such as the nauseating stenches.