Durable Magic (5e Feat)
From D&D Wiki
Prerequisites: The ability to cast at least one spell
You always seem to pull more mana out of the arcane plane then you need, as such you've learned to wrap yourself in a protective coating of it, rather then let it disperse.
-Your Intelligence score increases by 1, to a maximum of 20.
-While you maintain concentration on a spell, you have a +1 bonus to AC and all saving throws.