Superior Elemental Mastery

You have become a epoch in the use of a single element turning it into almost Divine-like damage. 

Whenever you successfully attack a creature with a Elemental damage type that you have Mastery in, that creature now takes your Spell attack modifier of that damage type as well.

Any creature that has immunity to the Elemental damage type you have mastery in, is now only resistant to it.

Also, your critical attack when casting a spell that deals elemental damage using your Elemental Mastery element now critically attacks on a 19 or 20 on a D20.