Sharpening Stone

“	Sharpen those darts, friend! Apply this to your darts and blades and they'll be sharper than ever before. Runs out after 10 rounds.	”
	^{~ Description of "Sharpening Stone" at Level 5-14}

“	Sharpen those darts, friend! Apply this to your darts and blades and they'll be sharper than ever before.	”
	^{~ Description of "Sharpening Stone" at Level 15+}

SharpeningStonePlus — Sharpening Stone Plus

Sharpening Stone is an item purchasable in Geraldo's Shop. Sharpening Stone serves as a tower buff that can be targeted onto any tower that contains the Sharp damage type by default. This effect lasts 10 rounds or is lost sooner if the tower no longer contains an attack with the Sharp damage type. Stock for Sharpening Stone regenerates every 5 rounds, up to 3 maximum units in stock. When first unlocked, Geraldo will stock only one Sharpening Stone.

If the tower lacks any attack with this damage type, the tower cannot be buffed nor affected by the buff. If the tower is upgraded to one without Sharp damage, it loses the Sharpening buff, though adding non-Sharp damage via a a tower buff (e.g. Acidic Mixture Dip, Permanent Brew's perma-AMD, Monkey Intelligence Bureau) does not negate the Sharpening Stone buff.

The buff lasts for 10 rounds or until sharpening conditions are no longer met. For instance, if transformed into a tower that lacks sharp attacks (with exception of Plasma Monkey Fan Club), the buff wears out permanently. It is possible to re-apply an upgraded Sharpening Stone buff, but not possible to re-apply the buff if said buff is identical or weaker to the existing one on the tower. If the tower lost the buff due to a temporary condition (e.g. Total Transformation monsterization), it can be applied a new Sharpening Stone.

Geraldo can sell Sharpening Stones starting at Level 5. Initially, Sharpening Stone gives +1 pierce. Once Geraldo reaches Level 15+, Sharpening Stone Plus is unlocked, empowering its buffs to +2 pierce instead of +1. As of release, towers which received the weaker buff do not automatically get the upgraded buff, but can be re-buffed.

It costs $170 on Easy, $200 on Medium, $215 on Hard, and $240 on Impoppable.

List of Buffable Towers[]

For a tower or hero to become eligible for Sharpening Stone, at least one attack from that tower must contain the Sharp damage type by default. Any attack that does not contain Sharp as the default damage type cannot gain the bonuses from Sharpening Stone. For instance, Geraldo cannot apply Sharpening Stone to himself (or other Geraldos, in Co-Op Mode), since the sole attack directly from Geraldo is his zapping lightning explosions (which have the Energy damage type). However, he can apply it to a Bomber Ace, whose darts benefit from Sharpening Stone but not its bombs (which have the Explosion damage type).

Crosspaths listed below are measured in terms of "crosspath availability".

2-5-4 Dart Monkey
5-5-1 Boomerang Monkey
Bomb Shooter with exactly Frag Bombs (x-x-2) crosspath only. Any other path 3 does not have Sharp.
2-2-5 Tack Shooter
1-2-5 Ice Monkey but only Icicles and Icicle Impale (Note: Icicles count) (Note: Icicles become Normal type with Cold Snap (2-x-x).)
0-5-5 Sniper Monkeys
5-1-5 Monkey Subs (Note: main darts count)
All Monkey Buccaneers except Navarch of the Seas (Note: main darts and regular grapes count)
4-5-5 Monkey Aces (Note: main radial darts count)
4-5-5 Heli Pilots (including mini-Comanche) (Note: main darts count)
2-2-1 Dartling Gunners
0-3-3 Super Monkeys
All Ninja Monkeys except Ascended Shadow (Note: shurikens count)
0-5-5 Druids (Note: including thorns and after-vines, but has no effect on spirit vines)
1-5-5 Spike Factories
5-5-0 Engineer Monkey (including Sentry Gun) (Note: nails count). (x-x-1 becomes Shatter type.)
2-1-4 Beast Handler but not 0-0-0 (Note: Crosspaths are independent in this particular case because the buff affects specific beasts)
Quincy (Note: Regular arrows count)
Level 3-15 Obyn Greenfoot (Note: Brambles ability only)
Captain Churchill Level 5+ (Note: Machine gun counts)
Admiral Brickell (Note: pistol counts)
Sauda Level 1-6
Geraldo's Shooty Turret

Note 1: Special MK that grants popping of specific bloon types (e.g. Hot Magic) does not revoke use of Sharpening Stone, as this does not modify the de facto default damage type. Similar reasoning applies for Relic Knowledge.

Note 2: The main tower can pass on Sharpening Stone to all its subtowers, even if the subtowers cannot actually utilize the buff. An example of this is Sentry Expert, which gives the buff to its sentries despite none of them actually having the sharp damage type.

Note 3: Etienne cannot be buffed by Sharpening Stone.

Strategy[]

Summary[]

Sharpening Stone greatly enhances effectiveness of sharp towers, especially those for Super Monkeys and Dartling Gunners without Powerful Darts, allowing them to gain a substantial amount of DPS increase. The pierce bonus of the base Sharpening Stone mainly works for the early-to-mid-game, which helps pop groups of bloons a little more effectively. Because the lifespan of the Sharpening Stone is limited, it is best to apply them whenever necessary rather than willy-nilly applying onto towers.

Once Sharpening Stone upgrades by leveling Geraldo to Level 15+, it gives +2 pierce, making it much stronger. It is especially powerful with upgrades that shoot many projectiles, such as The Tack Zone, Grandmaster Ninja, and Carpet of Spikes.

Tips[]

Remember to reapply Level 15's improved Sharpening Stone buff to towers, as reaching the level will not improve the buff that's already on existing towers, and the very long-lasting bonus pierce is usually worthwhile for the extremely cheap price. Note that the icon displayed above a tower is the same regardless of which type of Sharpening Stone was applied, in which case hovering with an improved Sharpening Stone will help distinguish which towers have the basic buff and which towers have the improved buff.
Towers with low pierce or low damage per shot, but with high projectile counts, benefit extremely well from Sharpening Stone. Prime examples include the aforementioned Tack Zone and Grandmaster Ninja, but also Super Monkey, (though losing out on Plasma Blasts can be more harmful) and middle path Dart Monkeys, particularly, of course the Super Monkey Fan Club and Plasma Monkey Fan Club (the latter of which, despite gaining Plasma type on its ability, still has a Sharp base attack, and thus is viable)
Transformed monkeys by Total Transformation can't be buffed, even if the original monkey has Sharp attacks. If transformed while the buff is active, it will automatically wear off, even if the ability does expire.
Sharpening Stone can only be applied, and remain applied, if the tower possesses a Sharp attack, and only affect that tower's attacks with Sharp damage type. The only exception is dart monkey transformed by Plasma Monkey Fan Club, whose ability retains the effects despite altering the damage type.
Sub-towers inherit the buff, but still only Sharp attacks can be buffed, even if there's icon on it.
For certain towers that do have a lead-popping crosspath, such as White Hot Spikes for Spike Storm or Carpet of Spikes, it is recommended to give them external lead-popping such as Monkey Intelligence Bureau or Permanent Brew to make up for it. Permanent Brew and MIB both do not remove the Sharpening Stone buff.

Candidates[]

Best Candidates[]

Sharpening Stone can be used optimally for the right purposes. Best candidates for Sharpening Stone include:

Overdrive and The Tack Zone - The vast amount of tacks produced at such rapid rates makes Overdrive a prime candidate for Sharpening Stone's pierce buffs. Its DPS becomes significantly stronger with the upgraded Sharpening Stone. Recommended to go for the 2-0-4 crosspath for optimized attack speed. Similar principles apply for The Tack Zone, albeit a lower magnitude of DPS improvement but a still appreciated bonus.
Destroyer + Grape Shot - Destroyers with Grape Shot shoot darts and grapes rapidly, making them a prime candidate for Sharpening Stone. As the grapes have very low pierce at base, this is a very large DPS increase, especially with the improved Sharpening Stone. Hot Shot does not work with this synergy, although it only changes the grape attack.
Bouncing Bullet - While individual bounces do not receive pierce buffs, the shrapnel produced with each bounce take advantage of the much greater pierce. Its enhanced DPS is much more noticeable if given the upgraded Sharpening Stone. Requires the Path 3 crosspath to optimally use it; Path 1 crosspaths revoke the buff, wasting the DPS potential of Sharpening Stone.
Elite Sniper - Similar reasoning to Bouncing Bullet, except much faster attack speed and shrapnel already pops a lot of bloons at base. However, the bullets themselves remain unaffected even with the upgraded Sharpening Stone. Requires the Path 3 crosspath to optimally use it; Path 1 crosspaths revoke the buff, wasting the DPS potential of Sharpening Stone.
Airburst Darts and subsequent upgrades - For the Path 3 Subs that are crosspathed with Advanced Intel, particularly Triple Guns, Armor Piercing Darts, and Sub Commander, the individual darts and bursted darts make great use of the improved pierce and damage (if using the upgraded Sharpening Stone). Does not work if crosspathed with Heat-tipped Darts.
Comanche Defense and Comanche Commander - Because the Sharpening Stone benefit works with mini-Comanches from Comanche Defense and Comanche Commander, the rapid fire darts from all helicopters synergize well with Sharpening Stone. It works best with Comanche Commander, as the mini-Comanches have full uptime, though it does work decently with the Comanche Defense too. Quad Darts also improves the mini-Comanches themselves, and hence the generally preferred crosspath for Sharpening Stone interactions.
0-3-x Robo Monkey - If not opting for Path 1 crosspaths, the Robo Monkey gains a significant amplification of its total popping power from Sharpening Stone. Naturally, a Robo with this interaction will be 0-3-1 or 0-3-2, which inflict knockback. Together, alongside the option to squeeze Robo Monkeys in tight spots with Worn Hero's Cape, the Path 3 Robos deal a lot of damage and general support in the late-game.
Aircraft Carrier/Carrier Flagship + Grape Shot - Similar reasoning to Grape Destroyers, with exception of the addition of aircraft, which produce darts and missiles. Like Comanche Defense, the aircraft darts from Aircraft Carrier / Carrier Flagship are also affected by Sharpening Stone. Hot Shot removes this synergy, although only for the grape attack.
Grandmaster Ninja and Bloonjitsu - As both options attack pretty quickly and shoot many projectiles per shot, these upgrades are solid candidates for the Sharpening Stone buff for the extra pierce. Recommended to choose the Path 3 crosspath to make use of the seeking attacks (via Seeking Shuriken) and the added caltrops (from Caltrops).
Spike Storm and Carpet of Spikes - If not opting for White Hot Spikes, this synergy works strongly with Spike Storms and Carpet of Spikes and their abilities.

Poor Candidates[]

In general, towers that already have huge pierce and/or have little to no projectiles are poor synergies with Sharpening Stone. Towers whose majority of damage comes from attacks whose damage types are not Sharp are also poor candidates (e.g. Master Bomber, as this only affects shurikens).

Bugs[]

Current

[33.3 (possibly 32.0, discovered in 33.3)] There is a bug whereby Sharpening Stone lasts indefinitely on Challenge Editor but not on normal games.

Patched

None (so far)

Version History[]

Balance Changes[]

Like many support-oriented items, Sharpening Stone was nerfed. For this item, it got a duration nerf to no longer last indefinitely, making timing of the stone become a key strategy instead of spamming the buff across towers. It was further nerf in Version 34.0, possibly to nerf his particular synergy with the popular Bouncing Bullet spam strategy on Expert Maps. Version 41.0 gave a nerf to the level 15+ stone, this time trading the +1 damage for +1 pierce.

31.0

Released

31.1

[bug fix] Geraldo's Sharpening Stone no longer increases the number of Bouncing Bullet bullet bounces, only the shrapnel
[bug fix] Sharpening Stone now correctly use Impoppable prices on Impoppable.

32.0

“	Many of Geraldo's items are too strong for the required maintenance, Geraldo SHOULD be a top level hero, he is literally designed to be so as the most rewarding for your player knowledge and reaction to moment to moment gameplay, but too many items reward spammable gameplay over these knowledge & reactions so we are targeting a lot of durations/stock amounts with minimal price increases where it feels necessary. These are clearly a lot of small steps, as we did not want to do too many big changes from multiple angles all at once.	”
	^{~ Ninja Kiwi}

[unimplemented] Sharpening Stone now expires after 15 rounds instead of lasting indefinitely
- Not implemented in 32.0 itself.

32.2 (?)

[implemented] Sharpening Stone now expires after 15 rounds instead of lasting indefinitely

34.0

“	Geraldo's Sharpening Stone still stands out as extremely powerful for such a low cost, [...]	”
	^{~ Ninja Kiwi}

Sharpening Stone round duration reduced 15 → 10

35.0

“	We just wanted to give some QoL	”
	^{~ Ninja Kiwi}

Sharpening Stone now has a stack count number, representing the remaining round duration

36.0

[Bug]: 00x Beast Handler does not benefit from Sharpening Stone whatsoever

38.0

Sharpening Stone no longer takes one more round to refresh stock if bought from full stock

39.0

Level 5-14 and Level 15+ Sharpening Stones will no longer stack their effects

41.0

“	We feel the higher level of complexity of Geraldo (along with simply much greater effort required to produce heroes like this) places him up on an elite tier of heroes we don't necessarily want players to jump right into before learning the game more, as we previously announced at the end of last year his unlock cost is now being increased to reflect this. A number of Gerry's items are also being tweaked here along with a base placement cost increase as he is also overperforming in a number of ways compared to other heroes.	”
	^{~ Ninja Kiwi}

Level 15+ Sharpening Stone no longer grants +1 damage
Level 15+ Sharpening Stone now grants an additional +1 pierce

Bug Fixes and General Changes[]

31.1

Geraldo's Sharpening Stone no longer increases the number of Bouncing Bullet bullet bounces, only the shrapnel
All Geraldo items now correctly use Impoppable prices on Impoppable.

32.0

Description of Level 5-14 Sharpening Stone now includes: "Runs out after 15 rounds." Doesn't apply to Level 15+ Sharpening Stone.

39.0

Lv5 & Lv15 Sharpening Stones can no longer stack their benefits

41.0

Modified Level 15 Sharpening Stone description to remove instances of bonus damage

Sounds[]

Applying a Sharpening Stone onto a tower:

[Sharpening blade]

Gallery[]

Videos[]

Version 31.0 Bouncing Bullet pierce with Sharpening Stone

Trivia[]

Sharpening Stone is the first, and so far only, item in BTD6 that can only affect towers of a specific damage type.
- Sharpening Stone is the first instance of affecting towers with specific damage types, the second is Flint Tips, which was added two updates after Geraldo's initial release.