(chiefly poetic) Relating to darkness or obscurity.

With insufficient light for easy discernment or comprehension

With a dark appearance

(figuratively) In a manner which is not readily visible or noticeable; inconspicuously

(figuratively) In a manner which retards or prevents discernment; clandestinely

(figuratively) In a manner which is difficult to understand, or which retards or prevents understanding; incomprehensibly

(figuratively) In a manner which tends to produce uncertainty or confusion; bewilderingly

(figuratively) In a manner which produces an inward conviction of future misfortune; ominously

(figuratively) In a morbid manner; morbidly, sinisterly