Boss Bloon Event/BTD6

Boss Bloon Events are events in Bloons TD 6 where the player fights off a Boss Bloon while also facing rounds of other bloons. Boss Bloon Events were first introduced in Version 27.0, starting with Bloonarius. Further bosses were added in later updates, with Lych being added in Version 28.0.

Playing against Boss Bloons in multiplayer via Co-Op Mode has been added in Version 28.0. This option is available whenever a Boss Bloon Event is active. In addition, Boss Races have also been added in Version 28.0, with similar gameplay to Race Events, except defeating the boss at all stages as fast as possible.

Bloonarius and Lych alternate each boss fight, first case of this being back in Version 28.0. The maps will also change each week.

Battles
The main structure of Boss Bloon Events is to beat all 5 Tiers of the Boss in order to fully win, beating all rounds is not required. Two variants of the boss exist, Normal and Elite. Elite is a harder version of Normal with more HP and greater rewards. Elite requires the normal boss to be beaten first.

Rounds will always be sent as if "Auto Start" was on, sending the next round as soon as the previous one finishes. This includes while the boss is active. Loading back into a game save will load the last completed round, but if the boss is active then the game will auto-continue.

Once the boss arrives, by dropping onto the track, the boss music plays, and the health HUD for the Boss Bloon will be visible. Rounds will still be sent normally, regardless of the Boss status. Rounds where the boss appears will be modified. Once dead, the boss makes a death animation and the boss music stops. The game then continues as normal, returning back to ordinary Auto Start. If the boss dies on its Tier 5 stage, the game is over and the player receives a win screen after beating the current round. The Boss Bloon must be destroyed within 20 rounds of appearance starting from the debut round, otherwise the player will automatically lose.

However, the player can lose to the boss in three different ways: losing all lives to non-boss bloons of any type (including natural bloons and boss minions such as Bloonarius Minions), leaking the boss with partial or full health, or failing to kill the boss within 20 rounds of its appearance no matter its tier. Instead of standard Continues, choosing a Continue while the boss is active will restart the player back to the earliest checkpoint in groups of 20 rounds. Continues will cost 100 every 20 rounds (e.g. losing on Round 40 will cost 200, and losing on Round 60 costs 300), up to 600 at Rounds 120+. Of course, the player can also press Restart to revert back to the first round. If the player loses while the boss is not on-screen (including rounds 1-39 and any grace periods before next boss tier spawns), Continues will be disabled.

Bosses each have a separate soundtrack, most of which are unique to a certain theme of boss. In Bloonarius Boss Fights, "Primal One" plays, while "Onslaught" plays while battling Lych.

Rewards
Rewards for one-off rewards may possibly change from week to week. Refer to for a list of one-off rewards. Rewards for the Ranked Boss is detailed here.

(Trophy rewards are formatted as / )

Main Leaderboard
Note that there is a special medal for placing in any of the categories in this section and Elite has its own separate special medals as well.


 * 1st Place: 1000, 40 / 60, 1 Power, 1 Tier 5 Insta
 * 2nd Place; 750, 35 / 50, 1 Power, 1 Tier 4 Insta
 * 3rd Place: 500, 30 / 40, 1 Power, 1 Tier 4 Insta
 * Top 50: 450, 25 / 30, 1 Power, 1 Tier 3 Insta
 * Top 1%: 400, 20 / 25, 1 Tier 3 Insta
 * Top 10%: 300, 10 / 15, 1 Tier 2 Insta
 * Top 25%: 200, 6 / 10, 1 Base Insta
 * Top 50%: 100, 3 / 5, 1 Base Insta
 * Top 75%: 50, 2 / 3, 1 Base Insta
 * Below top 75%: No reward

Mini Boss Leaderboard
Mini Boss rewards do not have special medals, just like the Mini Race.


 * 1st Place: 500, 15 / 20, 1 Tier 4 Insta
 * 2nd Place: 400, 10 / 15, 1 Tier 3 Insta
 * 3rd Place: 300, 5 / 10, 1 Tier 3 Insta
 * Top 10%: 250, 3 / 5, 1 Tier 3 Insta
 * Top 25%: 150, 2 / 3, 1 Tier 2 Insta
 * Top 50%: 100, 1 / 2, 1 Base Insta
 * Top 75%: 50, 1 / 1, 1 Base Insta
 * Below top 75%: No reward

Events
To find a list of every Boss event, view this article.

Assume start is Saturday 8:00pm NZST and end is Thursday 4:30pm NZST unless stated otherwise. Starting from Week 14, the end date is Thursday 4:30pm NZST to accommodate the added competitive leaderboards.

Below shows the latest 3 Boss Bloon events.

Co-Op Bosses
Co-op bosses behave similarly to regular bosses. There are multiple ways to play a Boss Event on co-op, either via the main Boss Event screen or through the "Play Social" button on the home screen. In co-op bosses, it becomes possible to get a higher degree Paragon, and generally becomes far easier to get higher degrees on Paragons. This is balanced out by increasing boss HP depending on how many players are in the game. 2-player fights will have 20% more boss HP, 3-player fights will have 40% more, and 4-player fights will have 60% more. Co-op does NOT increase the speed of the boss.

Completing a co-op boss grants the same rewards as solo play, and playing the same event solo after already beating it in co-op will not grant the rewards twice. Completing a co-op event in Ranked mode will also place the player in a completely separate leaderboard depending on the number of players in the game, detailed below.

Ranked Bosses
In Ranked Bosses, players compete in a global leaderboard for the fastest time for the event. Everything about the event remains the same except for the fact that Powers are disabled. (To avoid unfair Power use like Tier 5 Insta Monkeys or Cash Drops.) While the Boss is not on screen, a timer will start ticking 10 seconds (?) after the final Bloon in a round is sent and stops once the next round begins. If the player beats the round before this time limit, the timer does not begin. While the Boss is on screen, the timer will constantly tick until the Boss is defeated. The moment the final tier of the Boss is defeated, both timers stop counting and your final time is recorded. Co-op ranked leaderboards behave in the same way, where there's a different leaderboard for the number of participants in the co-op game. Large rewards are given to players who place well on the leaderboard.

Players are also entered into a "Mini Boss" leaderboard which is nearly identical to the Mini Race leaderboard. The player is automatically entered into a smaller leaderboard with only a max of 100 players. It has its own, smaller reward in addition to the main one.

Players can toggle on or off Ranked mode for Bosses in the bottom left of the main Boss Event screen. All players in a Co-Op match must have this option turned on in order to participate a Co-Op leaderboard, but it is possible for some players to quit partway through.

Summary
Farm super hard in order to save income for handling the boss. Always farm early as possible using Benjamin, Banana Farms or Merchantman. Each boss may have different properties depending on type, but most anti-BAD strategies should be powerful against Boss Bloons. Keep an eye on any special properties of the boss, as this may alter the way that boss needs to be beaten.

Tips

 * If not confident, boosting with a Cash Drop at the start to get a kickstart in massive greed may help.
 * Benjamin to kickstart income flow makes him the best hero for Boss Bloon Events.
 * Depending on the type of Boss Bloon, use different strategies for defeating them. Look at their underlying weaknesses. Strategies that work for BADs, with exception of instakills or health reducers, will likely work for Boss Bloons too.
 * The Ascended Shadow is one of the best towers to use, arguably more so than the VTSG. This is because the Sticky Bomb attack deals 96,000 damage at Degree 1 and about 384k at Degree 100. In addition to other attacks, that means this Paragon can deal insane DPS to bosses. It is less effective against Lych because of the etherealness, so be wary. Another downside is that it is the most expensive tower in the game in addition to being a Paragon.
 * Because bosses count for determining RBE on screen, and themselves pack with extremely high health, Avatar of Wrath triggers much more damage scaling than usual no matter the tier of the boss. This makes Avatar of Wrath an excellent choice for earlier tier bosses of any type. That being said, its value does wear off in much higher boss tiers due to capping its damage scaling at the 90,000 RBE mark for +30 damage.
 * A Vengeful True Sun God is not necessarily required for Boss Bloons. Players can simply pick out a True Sun God and compensate its weaker power with many Tier 5s and Paragons, or several max Sun Temples with plenty of buffs. A heavily buffed M.A.D. can also take down normal bosses with relative ease, and some earlier elite boss tiers.
 * This is especially helpful for players who do not have the Monkey Knowledge that would enable the VTSG, or if the necessary components for a VTSG are disabled.
 * Most Bosses will always begin on the very first path of a certain map. Test the map on Sandbox Mode and test a MOAB send on Round 1; the path where the MOAB goes is likely where the Boss may spawn from.
 * If desperate to use Powers, it is wise to invest in money-generating powers, especially Cash Drop and Thrive. To assist this, use of Banana Farmer for income assistance is beneficial, and Tech Bot for automatic assistance with ability activations is worthwhile. Purely offense-based Powers such as Super Monkey Storm or Road Spikes will be a waste of Monkey Money.
 * However, powers such as Monkey Boost and Energizing Totem are highly recommended as they can boost crucial towers DPS beyond boosts provided by Engineers, Monkey Village, and Alchemists, though be careful not to use these powers while Lych is on screen, as they will heal it greatly.
 * Time Stop essentially acts as a second Monkey Boost except for your abilities. As of Version 27.0, Time Stops will also slow down BADs and Boss Bloons to the same reduced speed as Towers. However, Paragons and abilities are also unaffected by the reduced speed which is one of the many reasons why Time Stop is a valuable Power to use here.
 * As seen on December 8th, (Lych or Bloonarius) boss fights can end earlier than normal, most likley because of an update release such as 29.0.
 * The Navarch of the Seas is a highly useful Paragon, arguably moreso than any of the others. Its hooks remove the threat of spawned/revived MOAB-class Bloons including BADs and overall deals massive damage to Bosses.

Trivia

 * Ninja Kiwi mentioned a conception of Boss Bloon Events back in their Version 15.0 patch notes for BTD6.
 * In Version 27.1, there was a bug fix where players are now given the correct increased trophy win for beating Tier 5 Elite Bloonarius. However, players who had beaten Tier 5 Elite Bloonarius prior to the update had to contact Ninja Kiwi manually to receive the 20 lost trophies from earning 50 instead of 70.
 * If the player reloads a Boss Bloon Event game with the boss active and bloons exit just before the boss theme begins, no music will play.
 * Rounds 101+ in Boss Bloon Events will still give 10% the normal XP despite the fact that it's not technically after the end of the mode.
 * According to Ninja Kiwi's 5th November 2021 blog, Ninja Kiwi states that they do not list Boss Bloon event results on their blogs to minimize bulkiness of the blog.
 * When Round 119 was made a fixed Freeplay round, it consisted of 2 (later 3) BADs. This is likely to build up to the Tier 5 Boss Bloon's appearance on 120.

History

 * Week 4's Boss Bloon Event had started from 14th August 2021 at 8:00pm NZST, and postponed from 15th August 2021 at ~3:50pm NZST until 16th August 2021 at ~2:30pm NZST. The event still ended on the same time, August 19th 8:00 NZST. This event became only available on version 27.3 due to a bug that caused boss retries to charge the player twice, and if done when the player can only afford one retry, would result in negative Monkey Money.
 * Week 12's Boss Bloon Event has been stated on the October 8th 2021 blog to end early on a NZ Thursday. Specifically, it's 13 hours early, and would end on 8:00am NZDT (New Zealand Daylight Savings Time), which would translate to 7:00am NZST. At the time, New Zealand was in Daylight Savings. However, the starting time was 9:00pm NZDT (or 8:00pm NZST without Daylight Savings) on 9th October 2021.
 * Between Week 9 and 11 (bottom-and-top inclusive), there was a bug where the hero in the rules menu would show "99" of a single hero, probably due to adding in a fixed hero between Weeks 6 and 8.
 * The first week for Lych, Week 13, did not include Psi, likely because of bugs related to Psi causing the game to softlock during Lych battles. It is not known the exact bug in question.
 * Since Week 16, Benjamin and Perma-Spike have become mutually exclusively available in Lych events. This ended in Week 24.
 * In Week 22, only 2 Dart Monkeys were allowed, preventing usage of the Apex Plasma Master; this may have been done to promote usage of other Paragons, especially the relatively new Navarch of the Seas at the time.

First Debuts

 * Week 21 is the first week to use a repeated map with the same boss, that being Skates with Bloonarius (Week 10 repeat). The second occurrence is Week 28, with In the Loop (Week 6 repeat).
 * Week 26 is the first week to use a repeated map with a different boss, on Cubism. Lych was featured on that week instead of Bloonarius, which debuted on that map during Week 5.
 * Week 25's Boss Bloon Event featured an Advanced Map for the first time, Cornfield, with Bloonarius as the boss.

Historical Statistics

 * There are a variable number of instances of each map difficulty appearing for each boss (valid as of 29th Boss):
 * 21 Beginner Maps
 * 8 Intermediate Maps
 * 1 Advanced Map
 * Unique maps bosses appeared (valid as of 29th Boss):
 * 19 Beginner Maps
 * 8 Intermediate Maps
 * 1 Advanced Map