Mangala, Mars, owns Vrishchika in classical jyotisha, his second sign alongside Mesha. A number of modern schools additionally treat Ketu as a co-lord of Vrishchika, on the argument that the shadow grahas should have signs of their own; this is a real disagreement within living practice rather than a settled point, and a reading that assumes Ketu's co-lordship without saying so is concealing a choice. The classical texts assign Mangala alone.
Chandra, the Moon, is debilitated in Vrishchika, with the exact low point given as the third degree. This is the mirror of the Moon's exaltation at the third degree of Vrishabha, the opposite sign, and the two facts are the same fact stated from either end. No graha is exalted in Vrishchika, so the sign carries a debilitation without a matching exaltation, the reverse of the situation in Vrishabha.
The nakshatras crossing it are the last quarter of Vishakha, then Anuradha entire, then Jyeshtha entire. Their vimshottari lords are Guru, Shani and Budha. Jyeshtha closes the sign and stands immediately before the gandanta, the junction between a water sign and a fire sign, which the classical literature treats as one of the most sensitive points in the zodiac. A planet in the final degrees of Vrishchika is therefore being read for two things at once, its condition in the sign and its proximity to that junction, and the second consideration often outweighs the first.