Each of Baldur's Gate 3's classes has different abilities and skills to aid them in exploration and combat. The Cleric class is a divine spellcaster who wield magic in the service of their god. Each of the Cleric Subclasses reflects a domain their god has dominion over, and grants the Cleric unique abilities relating to that domain.
Most of Baldur's Gate 3's classes only have three subclasses to choose from, but clerics are able to choose from seven options. The domains of Life, Light, Trickery, Knowledge, Nature, Tempest, and War all offer a cleric different abilities. A Cleric chooses their subclass at level 1 to reflect the power of their god's domain. What subclass they can choose is limited by the domains made available by their chosen Deity (which is also selected at level 1).
Life
Clerics of the Life Domain are likely what many players first think of when they hear the word "Cleric", wielding powerful restorative and curative abilities to keep their allies alive and in the fight. At level 1 they gain heavy armor proficiency to help keep them alive, and also gain "Disciple of Life." This ability causes all healing spells they cast to heal an extra 2+Spell Level HP. For example, this means a level 1 Cure Wounds spell would heal an extra 3HP.
At level 1 a Life Domain Cleric gains "Cure Wounds" and "Bless" as Domain spells, which are automatically and always prepared when resting.
At level 2 a Life Domain Cleric gains the ability "Preserve Life", which allows them to restore HP equal to their Cleric Level x 3 to an ally within 9m. This can be a powerful method of rapidly healing an ally during combat without using a spell.
At level 3 Life Domain Clerics gain the spells "Lesser Restoration" and "Aid" as domain spells. This allows the Cleric to remove diseases and conditions and temporarily increase their allies HP and HP maximums. At level 5 they gain "Revivify" and "Beacon of Hope" as Domain spells. "Revivify" allows them to raise dead party members, while Beacon of Hope will maximize healing received in an area while also granting advantage on wisdom saving throws and death saving throws.
Light
The Light domain is often granted by Gods of Justice and Fire, granting abilities that purge the dark and destroy the undead. At level 1 a Light Domain Cleric gains the ability "Warding Flare", which allows them to, as a reaction, impose disadvantage on an incoming attack. While this can only be toggled on and used once per turn, it still allows the Cleric to potentially evade a dangerous attack once per round.
At level 1 Light Domain Clerics gain the "Light" Cantrip as an additional Cantrip, and the spells "Faerie Fire" and "Burning Hands" as Domain Spells.
At level 2 Light Domain Clerics gain the ability "Radiance of the Dawn", allowing them to dispel magical darkness and deal radiant damage to all enemies within 9ft as an Action. This can be useful since magical darkness can't be penetrated by non-magical means, and the radiant damage is also very nice.
At level 3 Light Domain Clerics gain "Flaming Sphere" and "Scorching Ray" as Domain spells, allowing them a variety of methods to deal fire damage to single targets or large groups, and take advantage of flammable environmental hazards (like Grease.) At level 5 Light Domain Clerics gain the spells "Daylight" and "Fireball" as Domain spells too. Fireball is both self-explanatory and very powerful in combat, while Daylight allows the Cleric to enchant an object or create a sphere of sunlight, both of which will then emit sunlight that dispels darkness. Assuming this functions similarly to the tabletop game, the spell will be highly effective when dealing with any vampires that may appear in the full release, alongside its utility for exploration.
Trickery
The Trickery Domain grants powers of illusion and misdirection, and is a Domain granted by many chaotic and mischievous deities. At level 1 Trickery Domain Cleric gains "Blessing of the Trickster", allowing them to grant a creature in range (1.5m) advantage on stealth checks until the Cleric loses concentration. This can be fantastic when used in conjunction with a rogue, allowing them to easily scout ahead or dip out of combat to reposition and set up a sneak attack.
Level 1 Trickery Domain Clerics get "Charm Person" and "Disguise Self" as Domain Spells. The former allows them to gain advantage on skill checks in dialog or prevent a target from attacking in combat, while the latter allows them to change their appearance to fool NPCs and take advantage of special dialog options exclusive to a specific race. (A big example being interactions with Githyanki, who are notoriously difficult to interact with as any race other than Githyanki due to their severe superiority complex.)
At level 2 Trickery Domain Clerics can "Invoke Duplicity", creating an illusion that gives the party advantage on attacking enemies within the Illusions AOE, as long as the attacker is also inside the AOE. This, like Blessing of the Trickster, pairs incredibly with Rogues and their sneak attack to great effect.
At level 3 Trickery Domain Clerics gain "Mirror Image" and "Pass Without Trace" as Domain Spells, allowing them to increase their AC with illusory clones and give the entire party a +10 bonus to stealth checks. At this point the Trickery Domain allows players to make their entire party better at evading notice, and can be a fantastic support caster both in and out of combat.
At level 5 Trickery Domain Clerics gain "Bestow Curse" and "Fear" as Domain Spells. The Former allows them to inflict a wide range of curses with a touch, while the latter allows them to terrify foes into dropping whatever they're holding and fleeing.
Knowledge, Nature, Tempest, And War
These four subclasses for the Cleric are currently unavailable in the Early Access build of the game, so this information is derived from the tabletop 5e rules and, where available, announcements by Larian.
Knowledge Domain Clerics can channel divinity to read thoughts and become temporarily proficient in any skill or tool of their choice, and boost the power of their spells based on their Wisdom stat.
Nature Domain Clerics can channel divinity to charm animals and plants, learn a druid cantrip, and grant temporary resistance to elemental damage after a nearby creature takes damage of that type.
Tempest Domain Clerics can channel divinity to maximize the damage dealt by any spell that deals thunder or lightning damage, push foes away when they deal lightning damage to them, and cause thunder or lightning damage to a creature that attacks them as a reaction.
War Domain Clerics can make an extra attack as a bonus action a certain number of times each day, and channel divinity to grant a +10 bonus to their attack roll or the attack roll of an ally within 50ft.
These cleric types will gain appropriate Domain spells as they level up, though what these spells will be is not confirmed at this time.
Baldur's Gate 3 launches on the 3rd of August 2023 for PC and mac, and the 6th of September 2023 for PS5.