Flare

The Flare is a red stick with a gray head, found in the lockers of The Stairwell subfloor, where the wiki says it is most useful. It burns for 20 seconds and you can carry up to 3.

You light it with a left-click and throw it with a second click. Once thrown it flickers with red sparks like a Glowstick, and it leaves a glowing path that helps you avoid getting lost in the Stairwell. It also opens Meld walls when lit.

Quirks

• It is not counted as a light source, so it does not help with the "Enlightened" achievement. The wiki lists the Flare and the Moonlight Candle as items that emit light but are not treated as light sources.
• It has no effect on Creak's behavior.
• You can sell a Flare and receive 1 Scrap metal.

Compared with a Glowstick

Both are throwable light sources, but the Glowstick comes from The Mines in ten colors and stacks to 10, while the Flare is limited to The Stairwell and a single color. The Flare's role is orientation: the trail it leaves is the point, more than the light itself.