According to legend, whoever united it with the Resurrection Stone and the Cloak of Invisibility would be the Master of Death. It was said to be the most powerful wand that had ever existed and was able to perform feats of magic that would normally be considered impossible. For example, it was able to fully mend another wand that was thought to be damaged beyond repair.
It is fifteen inches long, made of Elder. It has a core of Thestral tail hair.
Harry Potter was the last master of the Elder Wand, Draco Malfoy being the previous master, then Albus Dumbledore before him who defeated the previous master, Gellert Grindlewald, in 1945. Grindlewald, in turn, stole it from the Bulgarian wandmaker, Gregorovitch who is the most recent master that the books mention.
Voldemort was in posession of the wand for a short period of time however he did not understand that to be the master of the wand you had to have won it from the last master, he stole it from Albus' grave not knowing that the wand alreadt trully belonged to Draco who had disarmed the headmaster before his death.
The power of the Elder Wand ended with Harry as it is mentioned in the books that he returned the wand back to Dumbledores grave.