Kosatsu

Kosatsu (the Princess of the Falling Snowflakes) is an ancient Bloon that was trapped in ice. She is the boss of the Desire & Ice special mission, and has 25,000 HP. She looks like a big white bloon with two pairs of ice wings. Like the E.N.T.I.T.Y. and other bosses, it just stays in the middle of the track. It is said that wherever Kosatsu goes, it badly snows.

Backstory

 * Eons ago, a devastating fight between the Princesses of Winter ocurred, which caused the Ice Age. They were eventually stopped by both of them, who exploded ice out of anger. Both ended up frozen deep in the coolest places of the Monkey World.
 * At the end of the fifth war, many populations were poor, so a couple of explorers decided to explore the Frozenfall Caves, near the Rink.
 * Those two explorers found an ancient frozen tomb, one of them accidentally left a fireplace on and it melt the ice where Kosatsu was trapped.
 * Whilst they were celebrating because they found an ancient tomb and would become rich, Kosatsu froze them, blew up the caves and flew to near Monkeyopolis City. She stopped halfway, near Monkey Lane.

Battle
When Kosatsu appears, she will stay 10 seconds "absorbing" energy, and the explode. The track will then transform into Snow Mode. She is immune to ice-based attacks and all attacks are Ice-type.

Kosatsu has many devastating abilities related to ice and freezing, proving that she is very powerful and focuses on letting her guys do all the job while she helps them.
 * Ice Beam: Shoots a bright blue beam that freezes a tower for 3 seconds.
 * Snow Fall: Snows everywhere. Due to the cold, all towers are slowed by 30%. Ice-type towers not affected.
 * Snow Guardians: Spawns 100 frozen Commando bloons. They will still move, but look and act like frozen bloons. The bullets deal twice damage to frozen towers. Bullets also have a 10% chance of freezing the target for 1 second.
 * Frost Shield: Selects 10 frozen Commando Bloons to surround and spin around her, reflecting both energy-based and sharp attacks.
 * Yeti Guards: Summons 5 "yetis" that will go near towers and punch them every 1.5 seconds, dealing 2 HP damage, 3 HP damage to frozen towers. The Yetis have 50 HP and move as fast as a red bloon. Can only be used if health is at 50% or lower.
 * Snowman Rangers: 1 minute and 15 seconds after the explosion, a snowman appears randomly on the snow ever 0.285 seconds and throws a single snowball that deals 3 HP damage to one tower and vanishes. Snowmen can't be killed. Lasts 12 seconds and can't be used again.
 * Subzero: Every tower in the screen is freezed for 5 seconds. Only uses this once when at 5,000 HP or lower.

Trivia

 * The BGM for the boss fight is Tire & Ice.
 * "Kosatsu" is a pun on "Kōsetsu" wich means "snow fall" in Japanese.  Subtle, ain't it?