Scything Blade Trap

From Xanathar's Guide to Everything, page 114.

Simple trap (level 5-10, dangerous threat)

This trap uses moving blades that sweep down through a chamber, threatening anyone nearby. Typically, a scything blade trap is activated by manipulating a lever or some other simple device. Kobolds especially like this kind of trap, since it can take down bigger creatures.


 * Trigger: When the lever is pulled, the trap activates.
 * Effect: Each Medium or larger creature in a 5-foot-wide, 20-foot-long area must make a DC 15 Dexterity saving throw, taking 14 (4d6) slashing damage on a failed save, or half as much damage on a successful one.
 * Countermeasures: The lever isn't hidden. A successful DC 15 Wisdom (Perception) check involving the surfaces in the trap's area of effect reveals scrape marks and bloodstains on the walls and floor. A successful DC 15 Dexterity check using thieves' tools disables the lever.