During the absence of Balarama in Dwarka (Srimad Bhagavatam, Canto 10, Chapter 65), Paundraka sent a message to Krishna, stating that the symbols used by the latter belonged to him, such as the flag of Garuda.
He declared he was the real Vāsudēva (God) and not Krishna, who is considered the Supreme Personality of Godhead.
According to the 66th chapter of Canto 10 of Srimad Bhagavatam, when Paundraka sent a message to Dwaraka, stating that he was God, Krishna declared war against him.
Paundraka's chariot was made similar to Krishna's, even with a flag of Garuda, after giving many warnings to leave his false claims of pretending.
The son of the king of Kashi, Sudakshina, created an evil demonic spirit using black magic to destroy Dwaraka, with the help of some corrupt priests.