Riṣṭa-Ariṣṭa

Riṣṭa is not just restricted to the native. It extends to mother, especially at the time of delivery, to siblings and parents and elders. Parashara teaches us various principles in the combinations to determine the evils for parents. Of particular interest is the durmantra combination in the previous lesson where the afflicted Moon in the 5th house can cause death of mother instead of the native because it is not in 1,7,3 or 9 houses. In the 5th house it is maraka (2H) from the 4th bhava showing the mother.
We learn three important principles

Riṣṭa Others

Bala-riṣṭa » 12 Years | riṣṭa associated with Moon as significator
Yoga-riṣṭa » 20 Years | riṣṭa associated with Jupiter as significator
Janma-riṣṭa » 24 Years | riṣṭa associated with Sun as significator

Duṣthāna Chandra
Duṣthāna Vakra-Graha
Durmantra
Tri-pāpa and Catur-pāpa
Maraṇa Kāraka Sthāna
Other Combinations explained
Tamas Chandra
Vināśa Yoga
Ardha Chakra
Shadow of Sun etc.
Things you need to study outside of BPHS
Tri-Pataki Chakra
Bear in mind that Neṣṭā Karma and Neṣṭā Graha require considerable understanding as these planets can surely give marriage and make life a wonderful experience or the converse i.e. living hell.
Riṣṭa (Evils