In Skanda purana, Kurma purana and Brahmavaivarta Purana they described about the hidden fact of, Ravana abducted Swaha instead of Sita to Lanka.
Every one know the story of the Ramayana but only few know that , the king of lankha, Ravana abducted Swaha, instead of Sita to lanka. This story clearly illustrates that no harm can be done to a person who is always intact with the truth of pancha bhutas (5 elements) which is the actual existence.
Sita asks Agni for help
Ravana disguised himself as a hermit and came to abduct Sita. On demand of hermit to cross Lakshman rekha to accept biksha, Sita got suspicious and prayed Agni to protect her if anything bad happens as she don’t want to deny biksha (food) to hermit . As soon as she came out of laksham rekha, Ravana appeared. Soon Agni took sita to Patala loka and replaced swaha, Agni’s consort in disguise of Sita.
Rama’s Promise to marry Vedavati
Indra’s act had special purpose behind it to avenge Swaha’s death, who was Vedavati in her previous birth. So, in reality Ravan had abducted Vedavati instead of Sita. Later on Rama
thanked Agni and promised that Rama would make Vedavati as his wife in Kaliyuga. The same vedavati has taken birth as Padmavati.
The return of Sita
So Ravana abducted Swaha and the entire war was fought over a Swaha who was not even real. After Rama won the war over Ravana, he took Swaha to ayodha. When the Test by fire (agni pariksha) happened, in the process, the Swaha (illusion) returned to the fire and the real Sita came out of fire. (The story of the Sita who was an illusion is also given in the Brahmavaivarta Purana).