In a gloomful manner; with gloom, sadness, or darkness.
From 'gloomful' plus '-ly' (the adverbial suffix), transforming the adjective into an adverb that describes how an action is performed or how something exists.
Adding '-ly' to mood-describing adjectives creates these wonderfully expressive adverbs—'gloomfully' lets you describe not just a state but the whole atmosphere of how something happens.
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