In Bloons TD 6, it is important to choose the best crosspathing for a specific tower in order to receive the best benefits out of that tower type. Towers have special roles to play for each stage of the game. The Alchemist in its core is to brew various potions to support the defense.
Alchemist can automatically pop lead bloons at its base and it is mainly used for support with all of it's paths. Crosspathing does have an effect on Alchemist. Path 1 focuses on giving Alchemist more support to monkeys through providing buffs, similar to the Monkey Village. Path 2 gives the alchemist more support by proving DPS to himself and eventually to other towers. Path 3 provides alchemist more support by providing another source of income. Similar to the ninja monkey, crosspathing only changes the Alchemist's main attacks, (that is, the potions it throws and except for X-2-X).
0-0-0: The second cheapest form of lead-popping but still quite a reliable source of such. Also possesses a damage-over-time effect that dissolves stronger bloons into weaker groups and pop weaker groups of bloons into nothing. This specific crosspath's main use is to deal with early Leads and their Black layers.
1-0-0: Even though it might seem like a simple increase in splash radius, this can be an important upgrade for higher tiers in other paths due to being able to apply its status effects to more bloons.
0-1-0: The acid's damage-over-time effect is quicker and lasts slightly longer.
0-0-1: This applies its splash effect faster
1-1-0: This allows it to apply its quicker damage-over-time effect to more bloons. It is also a stepping stone for 1-3-0 Alchemist.
1-0-1: This allows to apply the bigger splash potion effects faster. It is also a stepping stone for 1-0-3 and especially 1-0-4 Alchemist.
0-1-1: The applies its quicker damage-over-time effect at a faster rate. It is more of an uncommon crosspath due to Tier 1 being able to meaningfully affect its Path 2 and 3's higher tiers much more effectively.
2-0-0: Provides a buff that is a separate "attack" allows it to buff other tower to pop lead bloons and do extra damage to Ceramic and MOAB class bloons.
0-2-0: Cheap but effective at destroying Fortified MOABs, especially the ABR Round 40 MOAB. It defortifies Leads and Ceramics, and deals big damage to Fortified MOAB-class bloons.
0-0-2: It can put acid onto the track if there is no bloons nearby.
2-1-0: Its AMD isn't affected by the Stronger Acid upgrade.
2-0-1: Faster AMD shots too.
1-2-0: It is a 0-2-0 with a bigger splash.
1-0-2: The same thing as a 0-0-2 but its main attack now has a larger splash radius. Pools do not get affected by this crosspath.
2-2-0: It strengthens AMD by adding more shots per potion, and this crosspath can be used to strengthen Berserker Brew and Stronger Stimulant.
2-0-2: See 2-0-0 and 0-0-2.
0-2-1: Groups of 0-2-1 Alchemists can be used to inflict high damage to Fortified blimps.
0-1-2: Pools now have stronger acid. Usually a stepping stone for 0-2-2.
0-2-2: Pools now have perishing acid. This crosspath also affects the Acid Pool attack.
Upper Path 1[]
Berserker Brew[]
3-0-0: Crosspathing from here will be very useful, as making sure as many towers get the most uptime is important for the strength of Berserker Brew. It gives the alchemist a new type of "attack" that buffs the attack speed, range, damage, and pierce of the Monkeys affected by it. That being said, starting off with 3-0-0 helps get that headstart with boosting necessary towers.
3-1-0: This doesn't do anything in terms of increasing effectiveness of the buffs the Alchemist gives.
3-2-0: If you are planning to apply its buffs to a single stronger tower for longer, use this since the Alchemist can consistently keep the same tower with the brew buff for longer. Because of that, stronger buffs would allow the target tower to gain buffs for longer. Acidic Mixture Dip uptime on a single target also lasts longer. Additionally, adding a village to a 3-2-0 Alchemist can allow up to 2 targets brewed at a time, provided the closest target attacks relatively slowly (e.g. 3-2-0 Spiked Balls), even if the second target attacks quickly.
3-0-1: If you are planning to let multiple towers to have reduced but still reasonable uptime compared to 3-2-0, use this crosspath.
3-0-2: This doesn't do anything in terms of increasing the effectiveness of the buffs the Alchemist gives. All it does is add an Acid Pool attack, but upgrading a 3-0-1 to a 3-0-2 is a waste of money due to that attack's unreliability and not doing anything for its buffs.
Stronger Stimulant[]
4-0-0: The only thing that changes for Stronger Stimulant is that fact that buffs are stronger and last longer. In this case, it can consistently buff up to 2 of the closest towers. Again, crosspathing is very useful but not vital.
4-1-0:Same principles as 3-1-0
4-2-0: Both the Stronger Stimulant brews and Acidic Mixture Dips last longer, so a Stronger Stimulant with this upgrade can consistently keep brews and acidic mixture dips lasting for longer for each tower. Adding Jungle Drums allows it to brew up to 3 towers at most, provided its first two closest targets attack relatively slowly (e.g. 3-2-0 Spiked Balls).
4-0-1: Adding Faster Throwing will improve the brews by allowing to distribute brews fast enough to buff up to 3 towers at most, by default.
4-0-2:Same principles as 3-0-2
Permanent Brew[]
5-0-0: Permanent Brew makes the buffs of Stronger Stimulant's brew and Acidic Mixture Dip last forever. Because of this, all other upgrades and most of its own crosspaths are meaningless since now the player doesn't have to worry about the buff running out before it can buff other towers. In other words, it buffs all towers 100% of the time in its range, regardless of attack speed. Crosspathing for Permanent Brew usually depends on its predecessor, and crosspaths serve little importance to its main power with exception of 5-0-1 for a faster brewing rate.
5-1-0:Same principles as 3-1-0
5-2-0: Normally used as an upgrade to an existing 4-2-0 Stronger Stimulant. The brews will last forever, so this crosspath actually doesn't change how the brews work. However, 5-2-0 is very slightly stronger at offensive attacks.
5-0-1: Normally used as an upgrade to an existing 4-0-1 Stronger Stimulant. Usually better for this crosspath. This allows a Permanent Brew Alchemist to apply its permanent buffs to nearby towers at a faster rate.
5-0-2:Same principles as 3-0-2
Upper Path 2[]
Unstable Concoction[]
0-3-0: This upgrade coats MOAB class bloons with a liquid so that when destroyed, it will cause a large explosion to damage surround blimps. Note that the explosion does not damage its children. In terms of crosspathing, there is only two important upgrades to keep in mind, both of which directly affect the Unstable Concoction attack: 1-3-0 and 0-3-1.
1-3-0: Usually the better crosspath as its more efficient to than 0-3-2 and since the blimps move slow enough that the Alchemist won't chase the blimps.
2-3-0: Not very useful due to fact that the support it gives becomes more redundant the longer the game goes on since it doesn't scale really well.
0-3-1: If you need to catch faster blimps, use this crosspath.
0-3-2: This doesn't do anything in terms increase the effectiveness of the explosion's or rate of coating of blimps. Also, the Acid Pool attack only applies the normal acid, not concoction, as concoction is a separate attack and is not affected by the Acid Pool crosspath.
Transforming Tonic[]
0-4-0: Gains an ability that temporarily transforms it into a plasmatic laser-shooting monster, but disables all other attacks while the ability is active. Crosspathing does affect the ability, with top path tier 1 providing bonus pierce and bottom path tier 1 increasing attack speed. However, outside of the tier 1 crosspaths, it is functionally the same as Unstable Concoction.
1-4-0: Increases the pierce of the monster laser attack from 6 to 9. Does better against groups of bloons than single-target DPS. The overall better crosspath as rounds where you typically afford this upgrade (Rounds 55-65 more or less) and rounds after typically contain large rushes of ceramics, in which the higher pierce is frequently put to use.
2-4-0: Similarly to 2-3-0, the added AMD support potion is not as impactful as the monster transformation. However, note that transforming into a monster stops all other attacks including AMD while transformed.
0-4-1: Crosspathing increases attack speed of the lasers produced by the monster, outputting high DPS.
0-4-2: Neither the concoction nor the monster get affected by Acid Pool. As such, in essence it is just a 0-4-1 that has acid pools of 0-2-2.
Total Transformation[]
0-5-0: The transformation ability now affects itself and up to 5 nearby monkey-based towers up to Tier 3. As with Transforming Tonic, crosspathing does affect the ability, but only for this tower specifically. Even then, crosspathing doesn't really matter for this tower, as its main power comes from transforming Shinobi Tactics or Druids of Wrath which greatly overpowers this tower in terms of burst damage.
1-5-0: The weaker crosspath in general since at the point you can afford this tower, the pierce benefit for this tower is too big to make full, consistent use anymore. This is especially the case once health and speed ramping increases. In addition, the transformed mini-monsters gain a substantial pierce bonus already.
2-5-0:Same principles as 2-4-0.
0-5-1: Better crosspath since at that point, rounds contain huge health-ramped blimps that the faster attack speed can have better value.
0-5-2:Same principles as 0-4-2.
Upper Path 3[]
Lead to Gold[]
0-0-3: Going straight for 0-0-3 is helpful for quickly getting the benefit of its unique lead-conversion income generation effects and/or regular lead instakills.
1-0-3: Increases splash radius so that the Lead to Gold effect can be more reliable.
2-0-3: Does nothing to help Lead to Gold. In fact, it can do worse thanks to letting nearby towers steal lead pops before the Lead to Gold can do anything.
0-1-3: Does nothing to assist the Lead to Gold effect, merely just increasing acid strength for its main attacks.
0-2-3: Normally useless for income generation, but useful just as pure DPS. Mainly used as a DDT counter, although not as cost-efficient as other options.
Rubber to Gold[]
0-0-4: An Alchemist with Rubber to Gold regularly summons a gold potion that covers Bloons in a gold outline that gives bonus cash-per-pop similar to Monkey Town. Crosspaths change slightly for Rubber to Gold, with only 1-0-4 having any directly positive effect for its income production.
1-0-4: Generally the best crosspath for pure income. The gold splash is affected by Larger Potions, offering a greater splash radius and increased pierce.
2-0-4: Does nothing to help Rubber to Gold. In fact, it can do worse thanks to letting nearby towers steal lead pops before the Rubber to Gold's Lead to Gold effect can do anything.
0-1-4: Does nothing to assist any income-generating effect, merely just increasing acid strength for its main attacks.
0-2-4: This doesn't do anything in terms of increasing income generation. Simply more blimp damage and the same DPS as its previous upgrade.
Bloon Master Alchemist[]
0-0-5: The powerful shrink potion may look like it is affected by crosspathing, but it actually isn't. For crosspaths, treat BMA as if it was Rubber to Gold.
1-0-5:Same principles as 1-0-4
2-0-5:Same principles as 2-0-4
0-1-5:Same principles as 0-1-4
0-2-5:Same principles as 0-2-4
Strategy[]
Most of the Alchemist lacks vital crosspathing benefits, meaning that much of its upgrades don't depend so much on crosspathing for maximum value.