When Tārā assumes the qualities of Śiva, Kālī gets the counterpart - Śakti and when Kālī assumes the purpose of Śiva, Tārā becomes Śakti. The intelligent sādhaka as a result, should really in no way perceive any distinction between them and therefore gets liberated, by worshipping each and becomes https://www.youtube.com/watch?v=GMMWwN9ho2U&t=6s