First Last Line of Defense

 is a Support Monkey Knowledge point in Bloons TD 6, added in Version 22.0. It allows the first Spike Factory placed on the map to cost $150 less regardless of game modes. It requires One More Spike before unlocking this upgrade.

Prices
The following are prices for the Spike Factory with and without the effect of First Last Line of Defense: This discount applies to the first and only the first placed Spike Factory. Even if the player sells the first placed Spike Factory, the next "first" placed tower will be at base price.

Tips

 * In combination with More Cash, this MK allows a base Spike Factory to be usable as a starting tower on any game mode other than Hard or Impoppable.

Trivia

 * First Last Line of Defense is the first base tower discount-related MK to be released after initial release.
 * The word pun "First Last Line of Defense" likely refers to the fact that Spike Factories are mostly used near the exits to pop any Bloons that escape other towers, making them effectively the last line of defense. (The in-game description of the Spike Factory also explicitly calls it as such.) Since it applies only to the first Spike Factory that is bought, the name means it reduces the base cost of the first "last line of defense".