Choose a hero, place it away from the path, then upgrade it into its second form.

Select a placed hero to upgrade it. Max upgrades unlock Buff Bacon, Quickscope, Frost Golem, Juggernaut, and Commando Tank. Beat Level 1 to unlock Level 2. Level 2 enemies have thorns that reflect damage back to attackers. Chicky breathes fire, then summons two giant battle chickens in her second form.