SINISTERLY
Scrabble letter values: S1I1N1I1S1T1E1R1L1Y4 = 13
Definition
SINISTERLY is the adverb form of SINISTER.
adjective SINISTER: threatening or foreshadowing evil or tragic developments.
Synonyms of SINISTER: baleful, forbidding, menacing, minacious, minatory, ominous, threatening