If you are a writer or game master looking to deploy this trope effectively, avoid the "Deus Ex Machina" trap. The save must feel earned, even if the hero is dark. Follow these rules:

This makes the save more dramatic than any golden-haired knight charging a dragon. The knight doesn't understand what he risks. The dark hero does. And he does it anyway.

A gameplay-first representation where a broken, afflicted party of occultists, plague doctors, and thieves are the only line of defense against cosmic horrors. 5. The Psychological Appeal: Why Audiences Love It

If you want to avoid cliché with your "dark hero party save," avoid these mistakes:

Why is the dark hero saving this person? It cannot be "because it's right."

The dark hero does not fight fair. He fights to end the threat immediately.

: While the public praises a clean, marketable hero party, the dark hero party works in the shadows to eliminate the horrific threats the main heroes are too weak or naive to handle.