Complex sentence: The Elixir of the Wounded Heart is a powerful elixir capable of healing emotional and physical damage to the drinker's hearwas kept by Zelena, the Wicked Witch of the West, in the Emerald City's palace after she took it over.
Split into simpler sentences: The Elixir of the Wounded Heart is a powerful elixir capable of healing emotional and physical damage to the drinker's heart. In the past, this was kept by Zelena, the Wicked Witch of the West, in the Emerald City's palace after she took it over.