Answer: Foreboding
Step-by-step explanation:
According to the Oxford dictionary, foreboding means fearful apprehension; a feeling that something bad will happen.
From the sentence;
The shadows lengthened and crept out like stealthy, grotesque monsters across the grass.
The word which bests describe the underlying tone connotated by the words is “Foreboding”
The word grotesque means ugly
The word monster means a large frightening creature.
The word stealthy means secretive
The sentence translates to; the shadows crept out secretively like an ugly monster.
All these words put together give a foreboding description. That is they give a scary feeling and the feeling that something bad will happen.