Strategy:Alchemist (BTD6)

This article was last updated for: version 47.0

The Alchemist is a primarily support-focused tower. The top path focuses on buffs, the middle path focuses on damage, and the bottom path focuses on income generation, with the top path especially being a staple in almost every strategy. Its income generation from bloons is decent in early-to-midgame rounds with Lead to Gold and Rubber to Gold. Middle path and the lower-tier upgrades offers supplementary damage.

Path 1

Alchemist's top path is the most common use for this tower, giving buffs to nearby towers that boost their damage, pierce, attack speed, and range all at once. Berserker Brew especially is one of the strongest support towers in the game for its cost, being used in a wide variety of cases for any of its bonuses.

2-x-x Acidic Mixture Dip (AMD) gives lead popping power as well as extra Ceramic damage and MOAB-Class damage to other attacking towers. The base buff is applied to a random tower in range of the Alchemist every 10 seconds, and lasts until the target tower attacks 10 times. This means on average, one attack per second will benefit from the AMD buff, per Alchemist. If multiple Alchemists apply the buff to the same tower, the duration of how many shots will be buffed stacks additively, up to a cap of 50 attacks. When crosspathed, 2-2-0 Alchemist buffs last for 12 attacks, while 2-0-1 Alchemist buffs are applied 1.25x as often. At this tier, neither crosspath is worth its cost compared to just placing an extra 2-0-0 AMD.

AMD can find itself quite weak and inconsistent if the Alchemist is trying to buff thirty different towers, but it is also possible to focus a large number of AMD buffs into one strong tower that can make effective use of them. Other Alchemists, Glue Gunners that do not place glue puddles, Beast Handlers, and Psi cannot be targeted by AMD. If an Alchemist only has one tower that can receive the buff in range, it will only give the buff to that tower. And for a tower like Bloon Exclusion Zone, which attacks every 0.25 seconds for 4 attacks per second (4.7 with Stronger Stimulant, covered later), putting 5 AMD Alchemists nearby is enough to buff every single attack from that tower, letting them pop DDTs without needing the more expensive MIB while also boosting the tower's lategame damage. How feasible this is depends on the tower and the defense; Icicle Impale is a common target with its slower attack speed, but among other towers that would enjoy lead popping and the damage boost, Sun Avatar attacks far too fast to get good AMD buff uptime, while Grandmaster Ninja sits directly in the middle of several Shinobi Tactics that all divert AMD charges. AMD is one of a select few tier 2 or below upgrades that remains relevant and powerful throughout the entire game as long as it is tied to the right towers.

3-x-x Berserker Brew gives a far more powerful buff, which has a duration tied to either time or a number of attacks from the target tower, whichever comes first. With +1 damage and +2 pierce, this buff has the strongest relative effect on towers with low base damage and pierce, like Bloonjitsu or Overdrive, particularly as these cases shoot several projectiles at once while only using one shot of duration, but the 90% attack speed bonus (1.11x as many attacks in a given duration) means that any attacking tower can enjoy the bonus. When choosing a target, the Alchemist will give the brew to the closest valid target which does not already have a Berserker Brew buff or better. If all targets in range already have a brew buff, the Alchemist will wait and immediately throw its brew once a target's buff expires. This means that Berserker Brew can still function well even among several towers that can all accept the buff, as long as it is positioned closest to the tower that is supposed to receive the buff.

Berserker Brew buffs last for 25 attacks or 5 seconds, whichever comes first. For towers that attack less than 3.1 times per second, this means that buff time is the bottleneck affecting buff uptime, while for towers attacking faster than this, the shot count is the bottleneck. By default, a 3-0-0 brew gets 62.5% buff uptime on slow-attacking towers, while fast-attacking towers can see much lower uptimes. Hydra Rocket Pods, for instance, gets 37% buff uptime when accounting for the increased fire rate. Buffing the attack speed of both the buffing Alchemist and the target tower (usually with Jungle Drums) will increase buff uptime if time duration is the bottleneck, and leave uptime the same if the shot count is the bottleneck. With crosspaths, 3-0-1 applies brews 1.25x as often, while 3-2-0 increases the shot limit to 40 and the potion duration to 6 seconds. 3-0-1 has more impact on slow-attacking towers where the bottleneck is buff time, while 3-2-0 is better on fast-attacking towers that care more about the shot limit, with a tower that attacks 5 times per second being effectively covered by a 3-2-0 Alchemist.

Generally, the goal is to increase a tower's buff uptime up to, but not past, 100%. If the Alchemist has another potion ready, but the intended target still has a previous potion buff, the Alchemist will just buff another tower, turning a potential 100% uptime down to 50 to 60% uptime instead. This can still be useful, say if both towers the Alchemist is buffing are equally strong, but can often be a downside. The rule of thumb depends on Monkey Knowledge, as some Monkey Knowledge causes Alchemist to apply potions faster. Crosspathing a Berserker Brew is generally fine in CHIMPS or without Monkey Knowledge, but with Monkey Knowledge and Jungle Drums active, an Alchemist with either crosspath will split its brew across two towers.

Unlike AMD, Berserker Brew cannot be applied to the same tower for 5 seconds after the previous potion was given (4 seconds with x-2-x crosspath). This prevents spamming multiple Berserker Brews on one tower to get higher buff uptime on a fast-attacking tower like Sun Avatar. However, despite Sun Avatar's extreme attack rate giving it a very low buff uptime, it still greatly appreciates a Berserker Brew buff due to getting double damage and either 1.33x or 1.5x as much pierce for that short time, temporarily tripling DPS for far less than the cost of the Sun Avatar itself. Meanwhile, a few towers do not want Alchemist buffs due to not really benefiting from the buffs it provides. For instance, Psi barely gets a speed increase at all, as the speed of their attacks in mid-game and late game is determined by how long it takes Bloons to be destroyed, which is unaffected, while the damage buffs only affect resonance damage, a small part of Psi's damage output, and the pierce buffs do not let Psi grab additional MOABs in lategame.

4-x-x Stronger Stimulant improves the speed, range, and pierce buffs provided by Berserker Brew, but not the damage buff. The potion is thrown at the same rate of every 8 seconds, but its duration is increased to lasting 40 shots (55 with 4-2-0) or 12 seconds (13 with 4-2-0). However, this upgrade costs more than just placing another Berserker Brew, and placing a second brew instead also doubles AMD application. Its main use cases are when it targets a tower so expensive the 6% extra speed is worth the extra cost, a tower with low pierce that wants the extra point of pierce, or fast-attacking towers where the higher shot limit with 4-2-0 increases the buff uptime for one target tower. Used normally, the longer buff duration lets the Alchemist buff two towers at once, compared to one tower for Berserker Brew - the main concern here would be in the Alchemist diverting its brews into a third tower.

5-x-x Permanent Brew will apply the AMD and Stronger Stimulant buffs to all towers in range, with the buffs lasting forever provided the Alchemist is not sold. Due to its high cost, lower tiers are typically preferred during main game and especially in CHIMPS, but Permanent Brew is the only way to get 100% buff uptime on towers with extremely fast attack rates like Sun Avatar, and permanent AMD is strong as well. Crosspaths do not matter here as buff duration is no longer an issue. Other common pairs with Permanent Brew include Destroyers, Full Auto Rifles, and Druid of Wrath + Poplust spam. A Support Chinook can be used to move the Permanent Brew around the map to buff different groups of towers, most useful in Freeplay and Boss Bloon Events.

This upgrade path is actively detrimental against Lych, specifically, as Lych drains these buffs from towers and uses them to heal itself.

Path 2

Alchemist's middle path is the tower's best chance to stand alone as a damage tower, with early upgrades improving damage output, albeit needing cleanup towers to support them, and later upgrades giving them an ability that can deal a lot of damage, but has short duration requiring other towers to cover for the downtime.

x-3-x Unstable Concoction is a cheap source of damage in dense late game rounds that rides off of other damage towers. As blimps get popped, Unstable Concoction causes explosions that can rapidly open up several more blimps at once, getting massive damage relative to its price, but the Super Ceramics inside those blimps will be practically unaffected and start moving all at once. This upgrade needs both strong single target damage to start opening blimps for the explosions, as well as strong cleanup towers that can handle the massive amounts of Super Ceramics the explosions release, like Permaspike or Bloon Solver. 1-3-0 is preferred over 0-3-1 for the extra blimp covered per concoction.

x-4-x Transforming Tonic is a powerful tower for its cost, shining in both mid-game and late-game. However, its reliance on its ability limits its usability for Black Borders in CHIMPS, as getting the timing right for certain rounds can be RNG-dependent. At base, its ability uptime is 33%, with 40 seconds between casts that require other defense or stalling to cover for. Pierce is typically the main issue this upgrade runs into, and 1-4-0 does more group damage, but 0-4-1 does do higher single target DPS if that is more important.

x-5-x Total Transformation reduces the ability cooldown and adds the four nearest valid monkeys into the transformation. Used with random towers, its damage during the ability is less cost efficient than Transforming Tonic, but the extra transformed monkeys can receive tower-specific buffs that Alchemists cannot, like base Ninjas with Shinobis or Druids of Wrath with Poplusts. These tower-specific buffs make x-5-x a powerful late game win condition as long as the player can survive ability cooldowns. Plasma Monkey Fan Club is one option for this, as alternating between these two abilities can give 100% ability uptime. This tier has the same crosspathing tradeoffs as x-4-x, but with its overall higher power level, it has an easier time opting for 0-5-1 for the extra single target damage as its group damage is already great.

0-2-2 is also notable for building up a large amount of damage against isolated Fortified MOABs, which is helpful against Round 40 in Alternate Bloons Rounds but can otherwise be hard to make use of. Its poor consistency and insufficient pierce make it difficult to use for defortifying Ceramics in lategame, unfortunately.

Path 3

Alchemist's bottom path is focused around income.

• x-x-3 Lead to Gold is useful for money generation against Dreadbloon, which has custom rounds that greatly increase the abundance of Leads. It also can work well in Apopalypse depending on the round generation, or against rounds with many Lead Bloons like 37 and 38, but otherwise is overshadowed by the next upgrade.
• x-x-4 Rubber to Gold, on maps with one entrance, can generate twice as much extra money as a Monkey Town while stacking with it and other buffs, and being far cheaper. However, the money generation does not seep through blimp layers, requiring an instant kill such as XXXL Trap or Pirate Lord to profit off of them. Use with slowdown towers like Glue Gunners to clump and mark Bloons. The gold potion also removes all Bloon immunities, making it a niche solution to DDTs.
• x-x-5 Bloon Master Alchemist (BMA) struggles heavily against fast Bloons, is useless against BADs, and does not give any cash from converted blimps. Its damage also does not count towards several achievements nor the unlock requirements for Dartling Gunner or similar towers. This upgrade is not worth it.

Base

At base, Alchemist attacks bloons in an area and inflicts a damage over time effect against any Bloon type besides Camo. It is worse than an unupgraded Bomb Shooter for popping early-game leads such as on rounds 28 and 30, having slower attacks and being more expensive, but as a general damage tower it always does 3 damage to bloons it hits thanks to the lasting potion damage. Base Alchemist is very bad for cleaning up and against fast bloons, and should only be used with plans to upgrade it later.