illth (n.)

"what leads one to a bad state or condition," 1867, coined by John Ruskin from ill (adv.) on model of wealth (also see -th (2)).

[S]uch things, and so much of them as he can use, are, indeed, well for him, or Wealth; and more of them, or any other things, are ill for him, or Illth. [Ruskin, "Munera Pulveris"]