Leaves and stems:

The leafy frond, called a trophophore, is single near the top of the stem, oblong to spatula-shaped in outline, with 1 to 3 pairs of leaflets (pinnae). The trophophore is 1 to 4 cm (to ~1½ inches) long, held erect to ascending, its stalk .2 to 1.5 cm (to ~½ inch) long. The stem below the tropophore is 1 to 5 cm (to 2 inches) long. Pinnae are small, squarish to indistinct, mostly similar in size and shape. The tip may be rounded or straight across, the edge variable from smooth to irregularly toothed or notched. Plants are typically pale green and fleshy, almost succulent.

Spores:

At the top of the stem is the fertile frond, called a sporophore, usually 3 to 5 cm (to 2 inches) long, rising above the tropophore, the stalk portion .5 to 3 cm (to ~1 inch) long. Branches are few and very short, each with a few round capsules of spores (sporangia) that are partially embedded in the branch or stalk. Spores mature starting in July and may not be released until September.

Notes:

Little Goblin is only known from 3 states bordering Lake Superior (Minnesota, Wisconsin, Michigan) and in Québec, Canada. In Minnesota it is found almost exclusively in undisturbed, mature hardwood forest, usually in deep leaf litter, sometimes not even rising above the duff layer. According to the DNR, most Minnesota populations are concentrated in Chippewa National Forest in the north-central part of the state, but it's scarce even there. It was originally listed as a Special Concern species in 1984, with habitat loss and degradation from timber mining and land clearing posing the greatest threats, but since that time invasive earthworms destroying the duff layer have become a more serious threat. It was elevated to Threatened in 2013 and is currently listed as Endangered in Wisconsin.

It is most easily distinguished by the sporophore: few, very short branches with few, partially sunken sporangia that mature much later than most other Botrychiums. The tropophore typically has only 1 to 3 pairs of pinnae; pinnae are sometimes indistinct, more often squarish, rounded to straight across the tip, the edge smooth or irregularly toothed or notched. Plants tend to have a thick, succulent appearance.

Most similar is forest-grown Botrychium tenebrosum (Swamp Moonwort), which may also have very short sporophore branches with few sporangia, but sporangia are not sunken into the branch or stalk, it tends to have a longer sporophore stalk, rising well above the tropophore, larger pinnae that are often more rectangular (wider than long), and matures in the first half of summer, where B. mormo matures in the last half. B. tenebrosum is also found in more open spaces, not just under a forest canopy; those plants tend to have a much more robust appearance not easily confused with B. mormo.

Keep in mind that Botrychium identification can be difficult even for the experts so don't be discouraged if you struggle to get it down to species.