This special life bar is unlocked as a
gift when you complete all mini-upgrades (mandatory and optional) for that specific character!
If you have your tree fully completed, you will be able to claim the final level-up card!
And, if you are still progressing, you will see how far you are from having it available for your character, just access your tree by selecting your character, tapping on "Stats" and then on "Upgrades". Then all you have to do is scroll until the last card in the tree. It should show you the percentage that you have currently completed and how near you are from the 100%. :)
Keep on getting those mini-upgrades, Zoobster!
If you have your tree fully completed, you will be able to claim the final level-up card!
And, if you are still progressing, you will see how far you are from having it available for your character, just access your tree by selecting your character, tapping on "Stats" and then on "Upgrades". Then all you have to do is scroll until the last card in the tree. It should show you the percentage that you have currently completed and how near you are from the 100%. :)
Keep on getting those mini-upgrades, Zoobster!