THE DARK ROOM
torture & interrogation is a double-edged thing, imo. it affects the prisoners as well as the interrogators, and while t&i interrogators are a hardy bunch all around and do their job thoroughly, they're still human. with conscience and/or personal experiences/beliefs that may affect their ability to perform certain kinds of t&i methods required to extract information from prisoners that are more resistant to the usual brand of torture. not to say that they can't carry those methods out — just not for long, before something in their own psyche breaks down.
and konoha doesn't want that.
it's common knowledge that shinobi aren't the most psychologically-adjusted. those working for t&i are a different breed altogether, but even they have their own mental limitations. that's why t&i's turnover rate can get real crazy and a majority of their personnel are given mandatory leaves to re-calibrate after a few years. go into active rotation, do garden variety missions. live a semblance of a normal life. some don't even come back. and nobody can blame them. so now there's a select few (like tei) who are able to do whatever it takes without going batshit at the same time. a predisposition towards the gruesome and the nasty, sans the usual hair triggers.
the dark room itself is basically in the lowest level of t&i, sectioned off to cater to whatever needs to be done. the requirements for physical and psychological tortures are different, and they're designed for long-term confinement. some prisoners have been kept alive for years and are used as test subjects for torture methods, their bodies and minds broken and mended over and over again. the dark room operatives also work with anbu to train their recruits for t&i resistance.
and village traitors.
they love traitors down there. special treatment all around.
*to be revised from time to time