In a more dark or gloomy manner; in a way that is more characteristic of darkness or shadow.
From 'darkly' (the adverb form of 'dark') with the comparative suffix '-er', creating a double adverbial form that expresses greater degrees of darkness or gloominess.
This word rarely appears in modern English, which reveals something interesting: we prefer comparison phrases like 'more darkly' rather than '-er' comparatives for adverbs of more than one syllable.
Complete word intelligence in one call. Free tier — 50 lookups/day.