Defender

Defender
Many fighters wade into battle seeking fame and fortune, striking down mighty foes in search of ever greater glory. For some, however, there is no higher calling than the protection of the innocent from the ravages of evil. Stalwart shield in hand, these champions defend the weak from any who might threaten them.

Knight's Challenge
The challenge of a true knight is not an easy thing to ignore. Beginning at 8th level, whenever you damage an enemy with a weapon attack, you can use the Mark rules when making attacks. Additionally, if you damage a creature with a melee weapon attack while wielding a shield, you can inflict a Knight's Challenge upon it until the end of your next turn. You gain Advantage on opportunity attacks against a creature marked by your Knight's Challenge, and it suffers Disadvantage on attacks against creatures other than you.

Vigilance
A Defender's focus never wavers - their mighty strikes can hold back a legion of foes. Beginning at 13th level, you gain an additional number of reactions each round equal to your Wisdom modifier (to a minimum of one extra reaction).

Mighty Guardian
The greatest Defenders are titans on the battlefield - unflinching pillars of safety amid the chaos of war. Beginning at 18th level, while you are wielding a shield, you can wield a two-handed weapon on one hand. Additionally, you can use your reaction when an adjacent ally is attacked to grant that ally a +5 bonus to AC against the triggering attack. If this causes the triggering attack to miss, and if the triggering attack was a melee attack, you may make an opportunity attack against the offender as part of the same reaction.