Demon, husband of Vrinda, daughter of demon Kalanemi. Vrinda shared her mystical powers with her husband and Vishnu could only destroy him by intrigue.
Vishnu promised the terrified Vrinda to be allowed to live in his kingdom and to grow on earth as the Tulsi plant, the plant that is sacred to him.
In a similar story Tulsi is married with Shankhachuda.
Read about Jalandhara here