Ridiculous D&D contrivances

[KazilDarkeye]

A demon won't commit an evil act if it will destroy it (maybe a devil will, if it furthers the goals of other devils), and it is possible that it will risk destruction rather than commit an act of good.

It does, of course, depend on whether the fiend has high enough intelligence to realise that the evil act will do it harm. A Lemure would most certainly perish in these circumstances.