Shyamantak is a rare Indian name which is sounds similar to the word Syamantaka. Syamantaka, Syamantaka mani or the Syamantaka Jewel, is perhaps the most famous jewel in Hindu scripture, supposed to be blessed with magical powers.
Alternatively it could also refer to
God Krishna, (the eighth incarnation (avatar, or avatara) of the Hindu
god Vishnu), as Shyam(meaning dark, black and
blue) is another name for Krishna.