Darkness from chamber rewards

Chamber reward doors throughout Underworld escape attempts; spend collected Darkness at the Mirror in Zagreus’s bedroom.

Before you go

At each chamber fork, inspect the reward icon and choose a door marked for Darkness when it fits your route.
Clear the chamber encounter, then collect the reward that appears.
Continue checking door icons as you advance; reward types can vary by chamber.
After the attempt, return to Zagreus’s bedroom and open the Mirror of Night.
Spend Darkness on the rank you chose, then reassess what the next upgrade requires.

Treat the displayed icon as the deciding information: a blue laurel can represent Darkness, Keys, or Gemstones.
If a different resource is blocking a more useful account unlock, take that reward instead of collecting Darkness without a spending plan.

Repeatable on later escape attempts whenever Darkness appears as a chamber reward; the number of suitable doors varies.

Assuming every blue-laurel door grants Darkness; check the specific reward icon before entering.
Letting Darkness accumulate without a Mirror goal; choose a rank first and spend toward it.
Expecting to buy Darkness from the Wretched Broker; focus on direct reward sources instead.

Switch to Keys, Gemstones, or another displayed reward when a weapon unlock or Contractor purchase is the more immediate bottleneck.

Sources & fact checks

Open a guide to find other locations and see what the item is used for.

Run currency rewards

A repeatable way to fund Mirror of Night upgrades, especially before your first clear.