Ardra is the sixth, ruled by Rahu, its symbol a teardrop (sometimes a human head), its deity Rudra — the Vedic storm god who later becomes Shiva. The name means 'moist'.
Mechanically Rahu is magnification and obsession, Rudra the howl and the thunderstorm. Together: intensity. This nakshatra pushes feeling to its limit and at the limit breaks something open. In the hymns Rudra brings both disease and medicine, and that doubleness isn't a contradiction — the same rain ruins a field or saves it, and the difference is how long it falls. So Ardra is about the clarity on the far side of a storm: tears are water too, and what's been washed is clean.
Where you'll recognise it: high emotional intensity, a sharp understanding of pain, willing to say what others won't, clearer in a crisis than out of one, and often cleaning up afterwards for what you said. Running well, you're the one who penetrates: seeing people's pain, shattering the false, finding what's real in the mess. Stuck, intensity carries you off — destruction in place of expression, pain mistaken for depth, or living inside the storm and refusing to come out. Mrigashira before it searches; Punarvasu after it comes home: once the thunder has passed, a person needs somewhere to return.