Esther’s Talisman is a silver necklace which was created by Esther after being passed down by her mentor, Ayana. At some point before her death, Esther had handed the amulet down to her daughter, Rebekah, for safe-keeping.
During the early 1920’s as Rebekah and Klaus tried to evade their vengeful father, Mikael, Rebekah had lost the talisman during their flee. Stefan Salvatore found it, not knowing it was Rebekah’s due to Klaus’ compulsion, and gave it to Elena Gilbert many decades later.
After filling the amulet with vervain, Stefan had later given the necklace to his girlfriend, Elena Gilbert, who had worn the necklace throughout most of the series. Stefan filled the necklace with vervain because he didn’t want Damon, or any other vampires, to compel Elena.