Festivity Domain.

Worshipping deities of the Festivity domain spread joy and frivolity wherever they roam. If not kept in check, the most insignificant gathering can spin out of control to become a roiling crowd of jubilation as the cleric miraculously finds food and drink with which to incite a celebration.
Indeed, tales abound of clerics of Festivity infiltrating fortified citadels under siege, instigating exuberant carousing, and leaving their fellow merrymakers collapsed and exhausted after expending every last iota of energy. It is then a simple task for a waiting army to enter the city and lock their fatigued foes in chains. As the ancient proverb goes, “there is no celebration comparable to a cleric’s celebration, for a cleric’s celebration does not cease”.

Level 1 Features:

Festivity Domain Spells.

Each domain has a list of spells—its domain spells—that you gain at the cleric levels noted in the domain description. Once you gain a domain spell, you always have it prepared, and it doesn't count against the number of spells you can prepare each day.
If you have a domain spell that doesn't appear on the cleric spell list, the spell is nonetheless a cleric spell for you.

Reveller's Resilience.

You refuse to let your carousing be interrupted by something as trivial as a little pain. When you fail a saving throw to maintain concentration on a spell, you can use your reaction to reroll that saving throw. You can use this feature a number of times equal to your Intelligence, Wisdom or Charisma modifier (minimum of once). You regain all expended uses when you finish a long rest.

Life of the Party.

You’re an expert celebrant, armed with a plethora of tricks to liven up any party and a silver tongue to charm other guests. You learn the Flare cantrip. This doesn’t count against the number of cantrips you know.
In addition, you can use your Intelligence or Wisdom modifier in place of your Charisma modifier when making Charisma checks and Charisma saving throws.

Level 2 Feature:

Channel Divinity: Invoke Festivities.

You can use your Channel Divinity to conjure an atmosphere of celebration and merrymaking, lifting the spirits of your allies and imbuing them with the power of revelry. As an action, you present your holy symbol and choose up to three friendly creatures you can see within 30 feet of you and one of the festivals below. The chosen creatures gain the benefits of the chosen festival until the end of your next turn.
Blossom Festival.
You celebrate the growth of new life after the harshness of winter, and the beauty and vigour of youth. A creature regains 1d8 hit points at the start of its turn and deals an extra 1d8 radiant damage the first time it hits with an attack on its turn.
Midsummer Festival.
You celebrate long days and hot weather, as well as the sense of freedom they provide. A creature’s speed increases by 15 feet, and it deals an extra 1d8 fire damage the first time it hits with an attack on its turn.
Harvest Festival.
You celebrate nature’s bounty and reap the rewards of your hard work. A creature deals an extra 1d8 necrotic damage the first time it hits with an attack on its turn, and it gains temporary hit points equal to the necrotic damage dealt, which last for 1 minute.
Midwinter Festival.
You celebrate your community, banding together to endure the coming cold. A creature gains a +1 bonus to its AC and deals an extra 1d8 cold damage the first time it hits with an attack on its turn.

Level 6 Feature:

Afterparty.

Your celebrations have become so momentous that their effects linger even after they come to an end, leaving your allies invigorated and your foes exhausted. When a creature stops being under the effect of your Channel Divinity or a spell of 1st level or higher that you cast, one of the following effects takes place:
-If the creature is friendly to you, it gains 2d6 temporary hit points that last for 10 minutes.
-If the creature is hostile to you, it gains disadvantage on the next attack roll it makes within 10 minutes.

Level 8 Feature:

Potent Spellcasting.

Starting at 8th level, you add your Intelligence, Wisdom or Charisma modifier to the damage you deal with any cleric cantrip.

Level 17 Feature:

The Grand Revelry.

When you use your Invoke Festivities, you can choose to augment it, transforming it into the festival of the year. If you do, the effects last for 1 minute instead of until the end of your next turn, and, in addition to the friendly creatures, you can also choose up to three hostile creatures you can see within 30 feet of you, inviting them to take part in your celebrations. Each hostile creature must succeed on a Wisdom saving throw or suffer the following effects for the duration, depending on the chosen festival:
Blossom Festival.
The creature is charmed by you, and whenever it takes radiant damage, it takes an extra 1d8 radiant damage.
Midsummer Festival.
The first attack roll made against the creature each turn is made with advantage. Whenever the creature takes fire damage, it takes an extra 1d8 fire damage.
Harvest Festival.
The creature has disadvantage on attack rolls, and whenever it takes necrotic damage, it takes an extra 1d8 necrotic damage.
Midwinter Festival. The creature’s speed is reduced to 0 feet, and whenever it takes cold damage, it takes an extra 1d8 cold damage. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
Once you use this feature, you can’t use it again until you finish a long rest.