Marana Siddhi is a tantric rite to gain the ability or power to kill. This ability is used to kill and destroy enemies. Marana Siddhi is attained by those who have undergone rigorous penance.
Jnanarnavatantra, Dwitiyamundamalatantra and Mantramahodadhi texts contains detailed instructions about how the rite should be performed.
Mantramahodadhi text states that Bhadrasana is the posture useful for marana. The skin of buffalo is suitable for sitting.
Some scholars are of the view that, such Siddhis do not exist and is merely meant to scare people.