Sub-tower

A sub-tower is a tower created by another tower. Most sub-towers are temporarily created by an attack or Activated Ability from a parent tower (such as the Engineer Monkey's Sentries, which it builds with an attack that targets random positions within range) and disappear after a short time, though some last until their parent tower is sold or removed in some way, and some remain even if the parent tower is removed. Some sub-towers are selectable, allowing the player to see properties such as their range or targeting options, but not all. They do not have upgrades of their own, though some parent towers have upgrades that affect sub-towers (such as the Engineer Monkey's Sprockets). Most sub-towers have mechanics that interact with their parent towers, such as attacking sub-towers adding the damage they deal to the damage counts of their parent towers in addition to their own.

Classification

In the mobile versions of Bloons TD 5, Bloons TD Battles, and Bloons Monkey City, all air units (Monkey Aces, Heli Pilots, Aircraft Carrier planes, Phoenixes, and Radadactyls) are considered sub-towers. In the Flash versions of these games, none of these are considered sub-towers, meaning the only sub-towers are the Shadow Doubles in Bloons TD 5 and the Sentries in Bloons TD 5 Deluxe and Bloons Monkey City.

In Bloons TD 6, Bloons TD Battles 2, and Bloons Adventure Time TD, the air units of Monkey Aces, Heli Pilots, Rosalia in BTD6, and Marceline and Hunter Marceline in BATTD are not sub-towers. Air units receive all buffs applied to the tower's base, whereas sub-towers are not affected by Alchemist buffs.

In BATTD, sub-towers are classified as sentries, along with towers created by powers.

List of sub-towers

Bloons TD 5 / Bloons TD Battles / Bloons Monkey City

Image	Name	Towers / upgrades	Selectable?
	Sentry	Sentry Gun and further upgrades
	Super Sentry	Sentry Gun and further upgrades (Engineers Workshop only)
	Shadow Double	Ninja Monkey (Ninja Academy only)
	Fighter plane	Aircraft Carrier
	Monkey Ace aircraft	Monkey Ace
	Heli Pilot aircraft	Heli Pilot
	Phoenix	Summon Phoenix
	Radadactyl	Radadactyl
	Radadactyl Pro	Radadactyl Pro

Bloons TD 6

Image	Name	Towers / upgrades	Selectable?
	Fighter plane	Aircraft Carrier, Carrier Flagship, Navarch of the Seas
	Marine	Special Poperations
	Mini Comanche	Comanche Defense, Comanche Commander
	Phoenix	Summon Phoenix
	Lava Phoenix	Wizard Lord Phoenix
	Dark Phoenix	Magus Perfectus
	Sun Avatar	Sun Temple, True Sun God
	Spectre
	Storm Tree	Root of all Nature
	Trance Totem	Symphonic Resonance, The Final Harmonic	(selects parent tower)
	Sentry	Sentry Gun, Faster Engineering, Sprockets
	Crushing Sentry	Sentry Expert
	Boom Sentry
	Cold Sentry
	Energy Sentry
	Champion Sentry	Sentry Champion
	Green Sentry Paragon	Master Builder
	Red Sentry Paragon
	Blue Sentry Paragon
	Modified Sentry Paragon
	Beasts	Beast Handler	(selects parent tower)
	Nature's Ward Totem	Obyn Greenfoot (levels 4+)
	Sacrificial Totem	Ezili (levels 7+)
	Ball of Light	Adora (levels 10+)
	Drone	Etienne
	UAV	Etienne (levels 8+)
	UCAV	Etienne (levels 10+)
	Shooty Turret	Geraldo
	Creepy Idol
	Rare Quincy Action Figure	Geraldo (levels 2+)
	Bottle of 'Gerry's Fire' Hot Sauce (becomes a sub-tower of the tower it is used on)	Geraldo (levels 8+)
	Pet Rabbit	Geraldo (levels 10+)
	Genie Bottle	Geraldo (levels 12+)
	Paragon Power Totem	Geraldo (level 20)
	Spirit	Corvus
	Ambush Bot	Drone Ambush Network, Trigger Happy Drones, Oh Boy, I Can't Wait!

Bloons TD Battles 2

Image	Name	Towers / upgrades	Selectable?
	Fighter plane	Aircraft Carrier, Carrier Flagship
	Marine	Special Poperations
	Mini Comanche	Comanche Defense, Comanche Commander
	Phoenix	Summon Phoenix
	Lava Phoenix	Wizard Lord Phoenix
	Sun Avatar	Sun Temple, True Sun God
	Spectre
	Sentry	Sentry Gun, Faster Engineering, Sprockets
	Crushing Sentry	Sentry Expert
	Boom Sentry
	Cold Sentry
	Energy Sentry
	Champion Sentry	Sentry Champion
	Nature's Ward Totem	Obyn Greenfoot (levels 4+)
	Ocean's Ward Totem	Ocean Obyn (levels 4+)
	Sacrificial Totem	Ezili (levels 7+)
	Scratching Post	Smudge Catt Ezili (levels 7+)
	Drone	Etienne
	UAV	Etienne (levels 8+)
	UCAV	Etienne (levels 10+)
	Swarm	Beetienne
	Auxiliary Hive	Beetienne (levels 10+)

Bloons Adventure Time TD

Image	Name	Towers / upgrades	Selectable?
	Snow Monster	Monsters Of Snow
	Skeleton	Necromancy
	Candy Archer	Candy Archers
	Gumball Guard	Gumball Guards
	Candy Copter	Candy Copters
	Military plane	M.A.F.
	Jet fighter	Sidewinder Strike
	SMO	Moe
	Party Crasher	Party Crashers
	R/C Plane	Any character equipped with R/C Plane

Trivia

• Adora's Ball of Light is considered a sub-tower in Bloons TD 6, but not Bloons TD Battles 2.