On lawns, meadows, and grassy areas. Autumn. Common. Widely distributed in Norway, but not many records.

Pileus 10-35 mm across, conical with acutely pointed centre, campanulate with or without an umbo, convex to more flattened with a prominent, broad umbo, pruinose, glabrescent, translucent-striate when moist, sulcate, somewhat lubricous when moist, hygrophanous, black to dark brown in the centre, grey-brown to grey towards the grey to whitish margin, fading to dark grey to grey. Lamellae 17-25 reaching the stipe, ascending, narrowly adnate, sometimes with a short tooth, dorsally intervenose with age, dark to pale grey with the edge paler. Stipe 25-70 x 1.5-5 mm, hollow, straight or somewhat curved, fragile, equal or somewhat thicker towards the base, terete, with age sometimes somewhat depressed and fissured, pruinose at the apex, glabrous below, pale brown, grey-brown or greyish, darker below, the lower parts sometimes blackish brown, the base covered with long, coarse, flexuous white fibrils. Odour indistinctive, acidulous or somewhat raphanoid when cut, not nitrous.

Basidia 27-36 x 7-10 µm, clavate, 4-spored. Spores 7-11 x 5–6.5 µm, Q 1.5-2.1, qav ~ 1.7, pip-shaped, smooth, amyloid. Cheilocystidia 25-75 x 6.5-22.5 µm, fusiform, lageniform, subcylindrical or somewhat irregularly shaped, apically with a simple or furcate neck, sometimes also with few, very coarse excrescences. Pleurocystidia scarse, fusiform. Lamellar trama dextrinoid. Hyphae of the pileipellis 2-4.5 µm wide, covered with simple to very much branched, cylindrical excrescences, which tend to form dense masses and become gelatinized. Hyphae of the cortical layer of the stipe 1-3.5 µm wide, diverticulate, with terminal cells often hard to find, variously diverticulate. Clamp connections present at all tissues.

Mycena aetites is a member of sect. Fragilipedes, and is not always easy to identify. It can be found together withseveral other members of the section. M. leptocephala has a nitrous smell, smooth hyphae of the stipe cortex and typical, inflated terminal cells. M. parca also has smooth stipitipellis hyphae, and the cheilocystidia are more homogeneously lageniform. M. austera has a nitrous smell, smooth to sparsely diverticulate stipitipelliis, and large, conspicuous terminal cells in the pileipellis. M. aronsenii can be distinguished on account of the smaller spores, the hyphae of the cortical layer of the stipe which are covered with more or less curved to coiled excrescences and the coarsely diverticulate terminal cells. Mycena ustalis has smooth hyphae of the pileipellis, and M. cretata has long, hair-like caulocystidia. They both have a nitrous smell.