Sadko — Russian fairy tale character
Sadko is the principal character in a Russian medieval epic bylina. He was an adventurer, merchant, and gusli musician from Novgorod.
Sadko of Novgorod played the gusli on the shores of a lake and river. The Tsar of the Sea enjoyed his music, and offered to help him. Sadko was instructed to make a bet with the local merchants about catching a gold-finned fish in the lake; when he caught it (as provided by the Sea Tsar), the merchants had to pay the wager, making Sadko a rich merchant.
Sadko traded on the seas with his new wealth, but did not pay proper respects to the Tsar as per their agreement. The Tsar stopped Sadko's ships in the sea. He and his sailors tried to appease the Sea Tsar with gold, to no avail. Sadko realizes a sacrifice of a live soul was being demanded. All the shipmates drew lots, but Sadko draws the unlucky lot as if by fate or magic, so he is sent overboard and he sinks into the sea.