From Dragon Mania Legends (DML) Wiki
Portal Energy is the energy used on the Campaign Map for the Normal Mode and Heroic Mode campaigns each time a battle is fought. Portal Energy regenerates automatically at 1 unit every 25 minutes, up to the maximum base amount. It can also be recovered through purchasing with Gems (at the cost of 3 per energy), by leveling up or upgrading the Ancient Portal. Those methods fully replenish the energy; there is no option to select the amount of energy to replenish. The only way to replenish the energy in smaller amounts is to use small amounts at a time, and then a Trainer can replenish the amount remaining to maximum. The Portal Energy can be refilled by two different methods: by pressing the + button while on the Campaign Map, and by trying to engage a battle without any energy left (which will bring up the refill screen from where the energy can be refilled with Gems).
The base amount of energy is determined by the level of the Ancient Portal, the initial amount being three, while the maximum is nine. Trainers with an active VIP Status receive additional energy to their base amount. VIP levels 1-9 receive two energy units, VIP levels 10-18 receive three energy units and VIP levels 19-20 receive four energy units (thus the Trainer can have up to a maximum of thirteen energy units).
The total amount of energy a Trainer can have is unlimited. Any energy that is gifted or rewarded gets added on top of the current amount, which is displayed in green if overloaded (more than the base amount). Overloading stops the automatic regeneration of energy until the amount drops below the base amount again.
It costs 1 unit of energy to engage in a battle on Normal Mode and two units of energy for a battle on Heroic Mode. In addition to being used to start battles, Trainers can also opt to hire a friend's Dragon to aid in battles using Portal Energy.
The Portal Energy cost that is needed to hire Dragons from friends before going into a battle depends on the level of the hired Dragon. To engage in battle with a hired Dragon, the Trainer will need the amount of energy needed to hire the Dragon plus the amount of energy needed to commence the battle (1 in Normal Mode and two in Heroic Mode).
|Level Range||Energy Cost|
See Battle Energy for more information