Tier-5 Upgrades

Tier-5 Upgrades are special upgrades in BTD6. Unlike most upgrade tiers, only one Tier-5 upgrade per path per tower can only be bought once per game. Tier-5 upgrades are generally significantly more powerful than the respective Tier-4 upgrade. The icons and artworks for each Tier-5 upgrade are locked until they are unlocked through gaining enough Experience Points for any tower.

Bugs

 * When a Tier-5 upgrade is locked, in most occasions being due to maxing out in numbers of a specific Tier-5 tower, the upgrade description for the locked Tier-5 will be blank instead of giving a valid description of why the upgrade is locked.