For Solo:
Blunt Weapon Mastery - Increases physical attack power by 5% when attacking with a blunt weapon.
Undead Slaying - Increase your physical damage bonus by 20% when attacking undead monsters.
Perseverance - Reduces all types of incoming damage by 3.
Advanced Healer - Increase base magical heal by 5.

For Duo/Trio:
Advanced Healer - Increase base magical heal by 5.
Kindness - Heal yourself for 15% of the spell's total heal amount when healing another target.
Requiem - Resurrecting an ally revives them with 50% HP instead of a sliver of life. When reviving an ally at the Altar of Sacrifice, you don't need to sacrifice your own health.
Protection from Evil - The duration of all harmful effects is reduced by -50%.

For Solo:
Holy Purification - Inflicts 100 base magical damage to all undead monsters within 7.5 meters.
Spell Memory - Allows you to use spells in the dungeon.
For Duo/Trio:
Judgement - After focusing for 0.5 seconds, immediately deals 35 magic damage to a target and reduces their movement speed bonus by 20% for two seconds. Can only be cast when targeting an enemy within 4.5 meters. If the target gets out of range while casting, the casting fails.
Spell Memory - Allows you to use spells in the dungeon.

Protection - Creates a shield that blocks 20 physical damage for 20 seconds.
Bless - Target gains +3 to Strength, Agility, and Will attributes for 30 seconds. Casts to self if no target is found.
Lesser Heal - Heals a target for 15 HP. Casts to self if no target is found.
Divine Strike - Increases weapon damage by 10 for 20 seconds.
Holy Light - Heals an ally for 30 HP or does 100 base magical damage to an undead target.
Sanctuary - Concentrates on a specific area for a certain period of time, healing friendly beings within the area by 5 per second and dealing 14 spell damage to undead per second.
Resurrection - Target an ally to resurrect them from the dead. The corpse must have a soul heart.

Choose spells from the list depending on the amount of knowledge points and your play style.

As a Cleric, you can use a staff, spellbook, and mace, amongst others. It’s generally best to stick with the mace and shield combo for basic fights and switch to a magical weapon for healing, buffs, and magical attacks. The Spellbook comes highly recommended thanks to its high speed.

While the Cleric can use both heavy and light armor, a full plate set is usually suboptimal as it will make you very slow. Plus, you’re already well-protected by the shield. Mix and match plate armor with cloth and leather and prioritize pieces with the best stats.

Unlike the Wizard, the Cleric starts with a low Knowledge stat, which severely limits the number of spells you can use. Therefore, try to upgrade Knowledge first, and focus on Will and general damage bonuses next.

There’s no Dark and Darker class with better support abilities than the Cleric. It’s always a good idea to equip at least one healing spell and a couple of attack-boosting buffs. Although you can use them on yourself while playing solo, the Cleric is especially strong in a team formation.

Don't underestimate the value of bandages and healing potions though! After all, spells come with a limited amount of charges, and there's no such thing as too many healing options. Don’t forget to bring a Campfire either, as this will enable you to refresh your spells.

As a downside, the Cleric doesn't have the strongest physical attacks and is therefore heavily reliant on buffs. Their interaction speed and attack speed are very slow, so be wary of your time management, especially while playing solo.