Darkling \Dark"ling\, adv. [Dark + the adverbial suffix -ling.] In the dark. [Poetic]
So, out went the candle, and we were left darkling. --Shak.
As the wakeful bird Sings darkling. --Milton.
Source: Webster's Revised Unabridged Dictionary (1913)
Darkling \Dark"ling\, p. pr. & a.1. Becoming dark or gloomy; frowing.
His honest brows darkling as he looked towards me. --Thackeray.
2. Dark; gloomy. ``The darkling precipice.'' --Moore.