Defensive Caster

You have practiced casting spells to protect your allys, learning techniques that grant you the following benefits:

• You have advantage on Constitution saving throws that you make to maintain your concentration on a spell when you take damage.
• Any spell you cast that provides a bonus to AC or a flat AC are increased by +1.
• When an ally within 10ft of you provokes an opportunity attack, you can use your reaction to cast a spell. The spell must have a casting time of 1 action and must target only that creature or only the ally that provoked the attack.