Damar, a small hand drum. Around the diameter of a hand, it can also be a little larger.
Is played in Buddhist monasteries. Used as an instrument in tantric practices
Originally known as Damaru from India:
In Hinduism, the damaru is known as the instrument of the deity Shiva, associated with Tantric traditions. It is said to be created by Shiva to produce spiritual sounds by which the whole universe has been created and regulated.
The Indian Damaru and Mongolian Damar are made from wood.
In contrast, the Tibetan Buddhist Damar is made from the skulls of two people (Man and Woman). Religious practices are used to assemble the skull drum, for the stretched skin, and lettering. Called Skull Damaru or thod-rgna.
The more detailed practices of the skull drum are described in more detail on the Grinnell College Musical Instrument Collection website: https://omeka-s.grinnell.edu/s/MusicalInstruments/item/1516
The thod-rgna is supposed to keep evil spirits away.
A special bell or a human femur flute is usually played with the skull drum. I will go into more detail about this under the Tibetan musical instruments.
Since the main religion in Mongolia is Tibetan Buddhism (Lamaism), some instruments are also used in Mongolian monasteries.