Permafrost (BTD3-BTD5)

"Slows Bloons down even after they thaw out!"

- BTD4 description

"Makes the bloons so cold that they move slowly even after thawing out."

- BTD5 description

Permafrost is an upgrade of the Ice Tower in BTD3, BTD4, and BTD5.

It allows Bloons to stay slow once they have been unfrozen (50% speed for one layer, or two with the Deep Freeze upgrade purchased). It is also one of the cheapest upgrades in BTD5, next to Sonic Boom, and Long Range Darts.

Bloons TD 3
In Bloons TD 3, Permafrost is the 2nd upgrade for the Ice Tower, it costs $215 on Easy, $255 on Medium and $270 on hard.

Bloons TD 4
In Bloons TD 4, Permafrost is the 2nd upgrade for the Ice Tower, it costs $85 on Easy, $100 on Medium and $110 on hard.

Bloons TD 5
In Bloons TD 5, Permafrost is the 1st upgrade for the second path, it costs $85 on Easy, $100 on Medium, $110 on Hard and $120 on Impoppable. If combined with Sabotage Supply Lines and glue it will make a red bloon or lead bloon as slow as a ZOMG.

Strategy

 * Permafrost is a cheap upgrade to get to slightly boost your Ice Tower's capabilities, usually featured in extremely optimised strategies.

Trivia

 * In Bloons TD 3, this upgrade was called Perma Frost.