shadow realm

Etymology
The first sense is from, an invented place by for their English dub of the Japanese anime series  (2000–2004) as an ostensible place of suffering where people could be sent as a euphemism for. It does not exist in the original Japanese anime. Apparently based on Japanese, an actual location in the series which is also called the Shadow Realm in the English dub.

Noun

 * 1)  Oblivion; death.
 * 2)  Knocked out, rendered unconscious.