The Nun: a 5e Class

As musketballs whizz overhead and cannons belch smoke along the rim of the valley, a sister hospitaller drags a wounded soldier from the mud and leans him against a short stone wall, her healing touch weaving closed the bayonet wound in his abdomen... A Sister of the Cloistered Order of the Mother of Sorrows knocks a silvered arrow and takes aim at a rampaging werewolf, singing a battlehymn that infuses her shot with divine radiance... A barefoot sister of one of the wandering ascetic orders spreads jubilation across a marketplace, allowing her comrades- as if invisible- to free a Kirin a rich merchant has trapped on display... The harsh words of one of the Investigative Sisters of the Order of Saint Angela force a confession from the lips of a suspected kidnapper, leading to the rescue of orphans abducted by a fiendish cult!

Combining familiar elements of the Cleric, Monk and Paladin, the Nun is a half-caster support class with a playstyle all its own.  

At first level, you'll be able to rely on a talent from your Secret Past- perhaps you were a greedy artisan, a brave sellsword, a streetsmart urchin or a even a hardened criminal- a secular life you left behind to learn Songs of Faith and recieve a divine spark granting you the Armor of Faith and the ability to Channel Divinity and Lay on Hands.

You can throw yourself into a euphoric religious fervor known as an Ecstasy, reducing your capacity to experience pain and granting advantage on charisma checks and saves, almost like a barbarian in a rage through the strength of your convictions alone! Combining this fervent ecstatic state with your Aura of the Martyr, a Nun player will sacrifice her own hit points to spare others- and if, gods forbid, she is a felled by an enemy of good her Martyrdom will inspire her party to achieve great acts in her name.

The class has four subclass options, each following the teachings of a founding saint and creating vastly different character builds:

Order of the Hospitaller: The most Cleric-like of the Nuns, featuring a wide array of healing abilities and an Improved Lay on Hands.

Order of the Slayer: Your convent doesn't just pray for salvation- its nuns are trained to deliver it. Founded by a monster slaying saint, the militant sisters of your order accompany clerics and paladins on dangerous hunts for dark creatures of the night and protect small villages from undead incursions, their Battle Ecstasy imbuing their attacks with radiant energy and inspiring Acts of Faith.

Order of the Ascetic: Also known as Mendicants, these wandering vegetarian nuns eschew worldly pleasures for spiritual enlightenment, opening their Third Eye and allowing them to Perceive the Unseen. Unburdened and at peace, your laughter unleashes an Aura of Jubilation, and you can become the Center of Attention by pulling all eyes on you, allowing your allies to avoid detection. If attacked or defending the innocent, you can use your Defensive Martial Arts to thwart the violent and escape unharmed.

Order of the Disciplinarian: The sisters of orders dedicated to disciplinarian saints are blessed with Charisms, spiritual gifts or extraordinary power given by the divine- namely Wisdom, Knowledge, Counsel, Humility, Discernment of Spirits, Tongues, Prophecy and Fortitude- gaining access to all these gifts upon becoming a Living Saint at level 20. The Disciplinarian's Exacting Presence demands perfection from their allies as these sisters tax enemies with Chastising Words and Scornful Rebukes.