Heart of Vengeance (BTDB2)

Heart of Vengeance is the 2nd upgrade of Path 3 for the Druid in Bloons TD Battles 2. It is similar to its BTD6 counterpart except that it gives an immediate 20% attack speed bonus instead of an immediate 10% attack speed bonus.

It costs $300.

Summary
This upgrade adds an interesting dynamic that no other upgrade in the game does. It incentives the player using Heart of Vengenance to lose lives in order to gain a 1% attack speed bonus for every life lost which is what most players try to avoid. Note that 10 less lives have to be lost for the 100% attack speed bonus compared to BTD6; on a full 150 lives, leaking down to 70 lives maxes out the Vengeance boost for Vengeance Druids placed before any change in lives.

Tips

 * In terms of crosspathing, 0-1-2 offers the most DPS for upper path 3 upgrades while 2-0-2 can be useful for when the player wants to stop losing lives in order to not accidentally lose the game.
 * Get as many 0-0-2 Druids as possible as fast as possible, as this means that more Druids will get the attack speed buff while not in danger of dying.
 * Note that this mechanic is hard to utilize mid-game and beyond due to either the opponent sending eco bloons that are totally not going through or rushes that are supposed to kill the player and are too large to leak lives and survive.
 * Players that care about First Blood might want to stay away from this upgrade as properly optimizing this mechanic almost certainly means that the player will lose lives first.