Fully Charged Achievement in Immortals Fenyx Rising
Fully upgrade your Stamina.
How to unlock Fully ChargedStamina is upgraded at Zeus's workout area in the Hall of the Gods by spending Zeus's Lightning. You will need a total of 54 Zeus's Lightning to fully upgrade your stamina. The main way to obtain Zeus's Lightning is by completing Vaults of Tartaros. You will also get some Zeus's Lightning inside a few chests inside God Vaults, but these are not required. And lastly, you will get some Zeus's Lightning as rewards for completing some of the tasks on Hermes' task board.
As with ambrosia and Charon Coins, there is more Zeus's Lightning in the game than you need to fully upgrade your stamina, so you do NOT need to complete every single Vault of Tartaros. You will likely need to complete most of them though, with maybe around 10 or so being left incomplete. In terms of other achievements, be aware that there are tasks on Hermes's task board for completing all 10 arena Vaults, so make those a priority, and for obtaining all optional treasure chests in 22 Vaults, so ensure you always get the optional chests in all Vaults you complete. You also need to complete 10 hard (i.e. 3 out of 3 in difficulty) Vaults for a task. So make those your priority. Once you have fully upgraded your stamina and have completed those tasks for the task board, you can feel free to ignore all remaining Vaults of Tartaros, as they aren't needed for any achievements.