You have practiced casting spells in the midst of
combat, 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.
• You can perform the somatic components of spells
even when you have weapons or a shield in one or
both hands.
When a hostile creature's movement provokes an
opportunity attack from you. you can use your reaction to cast a spell at the creature, rather than making
an opportunity attack. The spell must have a casting
time of 1 action and must target only that creature.