Sentry Expert (BTDB2)

BTDB2

“	Sentries deploy with different damage types based on your need.	”
	^{~ BTDB2 description}

Sentry expert all special — Sentry Expert with all special sentries on screen

Sentry Expert is the 4th upgrade of Path 1 for the Engineer Monkey in Bloons TD Battles 2. Similarly to its BTD6 counterpart, it allows the Engineer to create specific sentries that specialize in popping different Bloon types.

The sentries that are used by the Sentry Expert from BTD6 are still used in Bloons TD Battles 2, specifically the Crushing, Cold, Boom, and Energy sentries. Algorithm for spawning sentries uses the old algorithm used in BTD6 before BTD6 Version 31.0, and the power of each one closely matches the Version 28.0 counterpart. Also, Crushing Sentries only have 16 pierce, 20 with 4-0-1.

Engineer will also immediately spawn 6 sentries when upgraded.

The Sentry Expert upgrade costs $2,800 and is unlocked with the purchase of Engineer.

Types of Sentries[]

There are four types of sentry that the Engineer may produce. All sentry types despawn after 25 seconds. All Sentries have 50 range and gain +4 range with Larger Service Area and +25% pierce rounded up with Oversize Nails. Deconstruction allows sentries to deal +1 MOAB-class and +1 Fortified damage, while Pin also gives the sentries with a pinning effect, even though none of their projectiles are made of nails.

Crushing Sentry[]

SentryCrushingPortrait — Crushing Sentry

The crushing sentry appears red and shoots spiked balls reminiscent of the Dart Monkey's top path upgrades, having both the bounciness and the same amount of pierce as Spike-o-pult. These balls deal 2 damage plus another +1 damage to Ceramic Bloons and are able to bounce off obstacles. It has a very slightly greater attack speed than Spike-o-pult and deals more damage to all bloons it can hit. Like Spike-O-Pult, Crushing Sentry cannot pop Lead Bloons without support.

Damage Type: Shatter
Damage: 2 (+1 to Ceramics)
Pierce: 16 (20 with 4-0-1)
Attack Speed: 0.91x (every 1.1s)

If Ceramic Bloons are present it will be the only sentry that can spawn.

Boom Sentry[]

The boom sentry appears black and is slightly larger than other sentries and shoots bombs reminiscent of the Bomb Shooter. Bombs pop bloons in a small radius (18 radius, roughly slightly less than the Ice Monkey's base range) and can pop frozen Bloons and Lead Bloons. The boom sentry roughly acts like a 2-1-0 Bomb Shooter with the attack speed of a Missile Launcher.

Damage Type: Explosion
Damage: 2
Pierce: 30 (38 with 4-0-1)
Attack Speed: 1.11x (every 0.9s)

If Ceramic, Black, Zebra or DDT Bloons are present it will not spawn.

Cold Sentry[]

The cold sentry appears blue and shoots snowballs reminiscent of the Ice Monkey's Cryo Cannon upgrade. Affected bloons are frozen for 1.5s and also gain the Permafrost effect. Snowballs pop and freeze bloons in a small radius, with a blast radius of 18. Cannot affect Whites, Zebras, or Leads. The cold sentry roughly acts like a weaker 1-0-3 Cryo Cannon.

Damage Type: Glacier
Damage: 1
Pierce: 15 (19 with 4-0-1)
Attack Speed: 0.67x (every 1.5s)

If Ceramic Bloons are present it will not spawn.

Energy Sentry[]

The energy sentry appears yellow and shoots red laser blasts reminiscent of the Dartling Gunner's Laser Cannon upgrade. Energy Sentry has the highest attack speed but the lowest pierce of any sentry. Laser blasts can pop frozen bloons but cannot pop Leads or Purples. It attacks a lot slower than any laser-related upgrade (i.e. Laser Blasts and Laser Cannon, the only two other upgrades with true lasers) but deals 2 damage and 8 pierce (or 10 with 4-0-1) each.

Damage Type: Energy
Damage: 2
Pierce: 8 (10 with 4-0-1)
Attack Speed: 1.75x (every 0.57s)

If Ceramic Bloons are present it will not spawn.

Strategy[]

Summary[]

Sentry Expert has a lot of different sentries specialized for popping various bloon types, however Sentry Experts sentries and the Engineer itself still cannot detect Camo Bloons without support, much like its BTD6 counterpart. The sentry-producing algorithm can be finicky when multiple bloon types are active at once, notably mixing Black and Lead Bloons together causing an insufficiency of Boom and Crushing Sentries. That being said, it works well in combination with a stable defense, such as a lone Captain Churchill, fulfilling extra damage and generalistic support DPS that the current defense wouldn’t be able to do alone.

It's ability to spawn 6 sentries at once on purchase can be used as a way to deal with heavy bloon rushes.

General Tips[]

The 4-0-2 crosspath typically performs better versus bloons, while 4-2-0 is better when dealing with MOAB-class and Fortified Bloons. Since damage values gained from Deconstruction give a bigger magnitude of total damage per projectile, the 4-2-0 is more impactful against those bloon types.
Upgrading to Sentry Expert before Round 11 begins is important for Round 11 defense, or else the sentries won’t build fast enough to provide anti-Purple and anti-Zebra sentries. This is particularly important for loadouts that lack any other suitable mid-game defender, such as the Engi-Farm-Super loadout.

Battle Tips[]

[1.0.5] TBA

Version History[]

Initial release (compared to BTD6 during Version 28.0)

Released

1.5.0

No longer requires 9,500 XP XP to unlock. Players who have unlocked this upgrade before the update will not receive a full refund.

2.0.0

Sentry expert red sentry spiked ball pierce reduced (22 -> 16)

3.3

Sentry Expert cost increased from $2,500 to $2,800
- Total price increase is $200 due to Sentry Gun (-$50) and Faster Engineering (-$50).

“	Engineer’s early game upgrades aren’t great, nor is 5xx. However, Engineer has some incredibly strong upgrades, being xx4 for a huge boost in cash and 4xx for easy mid-game defense. We have altered all of these upgrades, weakening its strong points while improving its weaker ones to compensate and balance it out.	”
	^{~ Ninja Kiwi}

4.1

Sentry spawn rate is no longer affected by attack speed buffs

“	[...] We have decided to change Engineer so that the spawn rate of its sentries can no longer be affected by attack rate buffs, but we have also greatly increased Sentry Champion’s regular damage so that it’s much stronger on its own now.	”
	^{~ Ninja Kiwi}

4.4

Sentry Expert will immediately spawn 6 sentries when the ungrade is first purchased

“	The Engineer has been languishing at the bottom of the “most used towers” list for a while. This change makes the sentry expert more useful immediately since it no longer needs to wait to generate its special sentry towers, and also opens up some interesting micro opportunities.	”
	^{~ Ninja Kiwi}

Gallery[]

Trivia[]

The nerfed upgrade cost of Sentry Expert is just like in initial release of Engineer in BTD6.