Rahu, which is the North Node of the Moon, is arguably the most dreaded planet in Vedic Astrology, even more than the usually discussed Saturn. Rahu is the head of a demon whereas Ketu which is the South Node of the Moon is the remaining (headless) body of the demon. While Rahu just like Ketu and Saturn is a naturally malefic planet, its malefic effects are more intense & overwhelming on people if it is ill-placed in their Natal Horoscope. However, such negative effects increase manifold when Rahu transits in a sign that is present in a house which is not a very conducive one for Rahu.