Master Defender

 is an upgrade in the Military Monkey Knowledge tree. It removes the 10 second cooldown from Elite Defender's attack speed passive ability, and will now always trigger the 4x attack speed ability provided that lives were lost within the past 7 seconds. It requires eight military knowledge points invested, Cheaper Maiming, and a one-time purchase of 500.

Summary
Mainly an ease that makes Elite Defender's life-loss ability less dependent on timing the purchasing of Elite Defender. Therefore, buying-and-reselling the Elite Defender just before bloons leak won't be as much of a hassle.

Tips

 * It isn't the best MK, but can be helpful as a bonus. This is mainly practical in the mid-game.