Fallen Feathers. Five of them are timed debuffs, while two of them are instantly applied upon infliction—but they’re all equally dangerous in the right situation. You should always wear gear that helps protect you against any status effects in the area you’re exploring,

The first "riddle door" you'll find in Wuchang: Fallen Feathers is found near the end of the starting region, Worship's Rise. You'll want to head down the main path from the Corpse Pits shrine and eventually enter the Tang Emperor Palace. As you progress through this area, there's a glowing red door that will pretty much be unmissable.