Here is the full list of all 15 Elementals Reborn achievements.
Get sapphire 5 league.
Get gold 5 league.
Get silver 5 league.
Get wood 5 league.
Unlock second tab of skill tree.
Craft a level 6 spell.
Craft a level 5 spell.
Craft a level 4 spell.
Craft a level 3 spell.
Complete 3 chapter of campaign.
Complete 2 chapter of campaign.
Complete 1 chapter of campaign.
Play 5 multiplayer games.
Reach a level 40.
Reach a level 20.