Arcane Stars can be obtained by opening Arcane Chests.
To open the Chests with Arcane Stars you need one of the five types of Arcane Coins.
Arcane Coins can be obtained from the Battle of the Strongest Challenge.
NOTE: A player can obtain and accumulate Arcane Coins from the Battle of the Strongest Challenge and Magic Pass rewards before player level 50, however, the Coins will be displayed in the profile only after reaching level 50.
Arcane Stars for any available Hero can drop from each Chest with a certain chance. You can get from 1 to 7 Arcane Stars at a time. The higher the level of the Chest, the more chance to get Arcane Stars of a higher level.
In addition, Arcane Stars can be upgraded directly with Silver or Gold Tokens, purchased with Arcane Coins.