Lockmaster Imps are the gatekeepers of the locked gates they guard in the console versions of Skylanders: Spyro's Adventure. They need to be moved about inside the lock in order to land them on top of the pink tumblers to unlock the gate. In the Ruins, you can find an imp next to a cave where you will find a Winged Sapphire, and afterwards recieve money everytime you solve the puzzle. They made a reappearance in Skylanders: Giants.
In Darklight Crypt, a fire ghost Lockmaster Imp appears inside the same lock the normal Lockmaster Imp is in, and moves slowly when the player rotates him. If the fire ghost Lockmaster Imp lands on the normal one, the green normal Lockmaster will burn away and you will have to start the Lock Puzzle all over.