Challenge rule

Challenge rules are modifiers to the game rules of Bloons TD 6. They are used in Daily Challenges, Race Events, Boss Bloon Events, Contested Territory, Boss Challenge, Boss Rush, Quests, and Rogue Legends. In Odysseys, they are known as island rules and are separate for each island. Players can configure challenge rules for custom challenges in the Challenge Editor and Odyssey Editor, but with constraints on some rules, and there are some challenge rules that are not accessible to the player and are only used in events.

Modifiers

Modifier			Effect
		Bloon speed	Multiplies the movement speed of non-MOAB-Class Bloons.
		MOAB Speed	Multiplies the movement speed of non-boss MOAB-Class Bloons.
		Boss Speed	Multiplies the movement speed of Boss Bloons. Not accessible in the Challenge Editor.
		Ceramic Health	Multiplies the health of Ceramic Bloons.
		MOAB Health	Multiplies the health of non-boss MOAB-Class Bloons.
		Boss Health	Multiplies the health of Boss Bloons. Not accessible in the Challenge Editor.
		Regrow Rate	Affects the rate that Regrow Bloons regenerate layers. Calculated by taking the reciprocal of the percentage and multiplying it by the 3-second delay between layers regenerating.
		Ability Cooldown Rate	Affects the rate that Activated Abilities recharge. Calculated by taking the reciprocal of the percentage and multiplying it by the cooldown.
		Removable Cost Rate	Multiplies the cost of removables and gizmos, or disables them entirely.

Rules

Modifier		Effect
	Monkey Knowledge Disabled	Disables all Monkey Knowledge.
	Selling Disabled	Prevents players from selling towers, except Champion Sentries, Sentry Paragons, Geraldo's Level 18+ Creepy Idol, and Special Poperations's Marine. Also disables Rare Quincy Action Figures.
	Powers Disabled	Disables all Powers (including Insta Monkeys) and Hero Boosters.
	No Continues	Disables continues.
	All Camo	All regular Bloons become Camo Bloons, including the children of MOAB-Class Bloons.
	All Regrow	All regular Bloons become Regrow Bloons, including the children of MOAB-Class Bloons.
	Custom Rounds	Indicates that the round does not use the default round set or modifies it in some way. Not accessible in the Challenge Editor.
	Double Cash Disabled	Disables Double Cash Mode.
	Fast Track Disabled	Disables Fast Track Mode.
	Paragon Limit	Restricts the number of Paragons that can be on the map at the same time.
	No Round 100 Reward	Prevents the player from earning Insta Monkeys for completing rounds that are multiples of 100. Not accessible in the Challenge Editor.

Special conditions

Least Tiers

In Least Tiers mode, the player is required to complete the challenge using a limited number of purchases. The tier count increases by 1 each time the player places a base tower, upgrades a tower, or levels up a Hero with cash.