From Dragon Mania Legends (DML) Wiki
See Arena Energy for more information
Arena Gems are used to fill the energy bar for fighting in the Dragon League. Each Arena Gem is the equivalent of one Arena Energy. Arena Gems can be obtained as a reward for 9 and 15 win streaks in the Dragon League and from opening Dungeon Chests. Arena Gems that are received are held in the tab of the inventory . The maximum number of Arena Energy that can be held in inventory at any given time is 20.
- Starting with Update 6.2 the win streak quantity required to obtain them changed to 9 and 15 from 6 and 12, and the maximum number of Arena Energy that can be held in inventory was reduced to 20.
- Starting with Update 4.6, they can also be obtained from chests in the Bottomless Dungeon.
- Between Update 1.4 and Update 2.3, they could be obtained by completing puzzles from Daily Quests.