The latest Destiny update The Taken King, introduces many secrets, and one of them are hidden locked chests that require keys to be opened. In order to get the keys you have to find Wormsinger rune first. Wormsinger rune is an item that attracts the attention of the Hive, and triggers new tasks.
It can drop off of any Knights or Wizards on the Dreadnaught.
How to use Wormsinger Rune
Head to Hull Breach and in one of the little caves you’ll see an object that you can use to insert Wormsinger Rune. It looks like a huge chest with green hive symbols on it. Once the Rune is activated you should see a text above your Super bar – The Hive summon a stalking party. Exit the cave and you’ll see numerous hive enemies and a Hive Champion that you have to kill. After defeating Hive Champion, he’ll drop “Wormfeeder Rune” item that you should collect. It’ll give you a task to kill 50 more enemies on the Dreadnaught without dying and it will convert Rune into a random key for a chest. The keys you get are random, but the corresponding chest for the key is usually very close to the place where you finished the Wormfeeder Rune task. The key also has a hint in its description to chest location. You lose Wormfeeder Rune if you boost to orbit.