Rune converts into Keys. To get Rune you need to defeat enemies by doing Patrol in Dreadnaught. Rune drop is Random. The Rune will randomly transform into 1 of 9 keys.
Example: I have killed enemies in Hull Breach twice & then Wormsinger Rune dropped. I headed to the cave i.e. (Start patrol on Dreadnaught. After you spawn, jump off the ledge ahead to the lowest level. Turn around, and go into the hallway. Turn right at the first crossroads, and you’ll see the chest by the wall.) Now use the Activated Rune in chest. 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. I got Key of Ur.