I've heard rumours that Esther is in the fourth coffin, well if this rumour is true here is my threory...
When Esther was the Orignal Witch back when her family were human and she had talked with Ayanna, but Ayanna said she would have no part in it, meaning she wanted nothing to do with Vampires. So when Esther turned her family into Vampires and saw them adapting. She wished she could turn too, so she went to speak with Ayanna, but Ayanna refused to speak to Esther. Esther was furious at her past friend, so she called upon the spirits and asked them whether it was possible for her a Witch to become a Vampire. The spirits kept silent, but Esther pleaded with them, eventually the spirits told her that if she were to become a Vampire there would be dangerous consquences and that during the ritual she had to complete, she may not see it throught till the end. But Esther did not care she wanted to be with her family so badly so went ahead with the ritual only telling Niklaus. Niklaus gave her his blood and Esther drank but because Niklaus was a Hybrid, the blood was not pure Vampire blood so as Esther began the ritual to turn herself into a Vampire. Halfway through the ritual, Niklaus noticed there was something wrong and tried to get Esther to stop, but she was in deadly looking trance. When she awoke from the trance she felt normal, Niklaus then plunged his sword through her heart to finish the ritual. Unbeknownst to them Ayanna was watching she had cast a spell so that Esther would never wake, she would be held in a deep sleep forever until her talisman woke her. That talisman was Elena's necklace, that was why it held it's own magic, it was Esther's magic and in order to wake Esther you need to take the life essence (that was placed in the necklace by Ayanna) and fed it to Esther. After that she will awake.
Thanks for reading. Please comment.