Introduction
Elemental Mastery is the reaction between elements during a fight. When you put a Pyro skill and Cryo skill for example, you will see the world "melt" pop up. That is the elemental mastery coming into action. When you upgrade it, the damage it gives increases. It can give insane damage to enemies if you are playing your cards right.
Should you Upgrade?
Yes, you should definitely upgrade your Elemental Mastery whenever you can. It can greatly increase your power with combos, and attack in general. It won't effect your attributes, but you will see the great increase of damage while in battle.
How to Upgrade
There is only 1 way that I know of upgrading this. That would be by using special artifacts. They are easy to come by, but be sure to enhance them as much as possible, so you can get the best results. If there are any other ways that I am missing, be sure to let us know in the comments!
Further Questions
If you have any further questions about this topic, don't hesitate to comment and ask! I will try and respond with an answer to the best of my ability!
Thanks for reading!
Happy Leveling!!