The new skins button
Skins is a feature, introduced with the Celestial Patch (24th Nov, 2017), which lets you alter the appearance of a selected range of heroes while granting them bonuses while wearing the skin.
They can be acquired as universal shards from defeating bosses on Celestial Island. The loot is usually 2 shards, and a total of 10 fragments are required to craft a skin.
Available Skins
King of War Asmodel
Last Wish Demon Hunter
Arctic Blade Blood Blade
Champion Golden Sword Iceblink
Black Warrior Das Moge
Arrival of Demon Barea