Pitch Black

Pitch Black is challenge #1. During this challenge, Curse of Darkness and Curse of the Unknown will be permanently active. Unlike other challenges, treasure rooms are available, but shops are not. The goal is to defeat Mom. This challenge is unlocked by default.

Difficulty
The curses inflicted are typically trivial on their own, however, they are the primary source of difficulty in this challenge due to the permanence of Curse of the Unknown, making it much more difficult to keep track of Isaac's health. This also makes it especially risky when using mechanics that drain Isaac's health, such as devil deals or blood donation machines. Additionally, Curse of Darkness, although mostly just thematic, does contribute to the difficulty of the challenge by making it harder to spot tinted rocks, which normally would aid Isaac's survival with soul hearts.

Strategy
While Devil deals can provide powerful items, taking one is very risky unless Isaac's health is carefully tracked. Refraining from deals can give access to angel rooms, which can provide items without the need to sacrifice health.

Turning the gamma setting up in the options can lessen the impact of Curse of Darkness.

While entering one is not recommended, finding a door to a Boss Challenge Room can at least gauge Isaac's health by checking whether it's open or closed.

Amnesia pills don't incur the Curse of the Lost, thus being one less bad pill to worry about; with an amnesia pill will also drop Black Heart on use for free.