The state of being sinister or evil.
Sinisternesses are very bad and scary.
Examples:
The haunted house was full of sinisternesses.
The movie had a lot of sinisternesses in it.
She felt the sinisternesses in the dark forest.
The sinisternesses in the story made me shiver.
The sinisternesses of the old castle were legendary.
The sinisternesses of the villain made the story very scary.