Example: "Insidious pleasures"
Example: "Glaucoma is an insidious disease"
Producing harm in a stealthy, often gradual, manner.
Intending to entrap; alluring but harmful.
Example: "Hansel and gretel were lured by the witch’s insidious gingerbread house."
Treacherous.
Example: "The battle was lost due to the actions of insidious defectors."