Pusillin is an imp mini-boss residing in Dire Maul East. Pusillin stole Azj'Tordin's book of incantations. His initial location is near the main entrance to the instance. Talk to him, and he skips away.

How do you get a DM key?

To get the key you must enter the main entrance to Dire Maul East. You will find a little imp named Pusillin. He is friendly at first so talk to him and you will need to chase him around the instance. Don't worry if he gets too far away, he stops every so often so you can fight the mobs to catch up.

Can you get crescent key solo?

The Crescent Key for DM North and DM West can be obtained with a quick jaunt into DM East. Although geared/skilled rogues or druids may be able to solo this, it's recommended to bring a group.