This build will focuses largely on using the gauntlet and class spells. In Lords of the Fallen, magic plays a more supportive role and being the traditional spellcaster is not possible in this RPG. This however does not mean that you cannot get as close as possible nor that magic is not a viable alternative to pure melee.
There are three magic based classes in the game. The Brawler, The Executioner, and The Cleric. They each use Brawling magic, Deception magic, and Solace magic respectively and all three classes focus on using magic. The two main attributes to worry about if you pick these classes are Faith and Vitality, but that does not mean that other attributes cannot be raised for your preference. Picking any of these three classes gives you the same starting gear. This guide will assume you pick Cleric as your class, but the other two can still get some benefit from this guide.
Strength: This is a useless attribute for our caster build as this attribute only raises damage with strength based weapons and increases carrying capacity a little. Do not bother with this attribute at all unless you wish to focus on using strength based weapons.
Vitality: This attribute is important to all classes and builds unless you want to run a low health build which I do not recommend. That would only be possible if you wear light armor and use light weapons so you can get a quick dodge. Since we will not be doing that, you should raise this to 17. You can go higher if you are playing a Brawler or plan on using a lot Brawling magic.
Faith: This is your most important attribute. It not only increases the damage you do with faith based weapons (which are called magical weapons in the game), but it also increases your mana bar which allows you to use your gauntlet far more often. It also allows you to learn the magic associated with your class as well. You should shoot to get this attribute to at least 40 before you go into NG+. If you are instead focusing on using Strength or Agility based weapons, then you should only increase this to at least 20.
Endurance: This attribute is semi important to a caster build. Endurance increases your stamina/energy bar and also your carrying capacity. While this may seem non important for a caster, since we will be wearing medium armor and using hammers, we will need the endurance to be able to carry and use them effectively. Unless you plan on using light armor and weapons, try to get this attribute to at least 15 and no higher than 17.
Agility: This another useless attribute for our caster build. It increases damage with agility based weapons and slightly increases the stamina bar. Just like with strength, ignore this attribute unless you plan on using agility based weapons like the staff.
Luck: This attribute only increases the item drop rate of enemies. This is not that important at all if you ask me, but you if you want to raise I suggest using attribute point shards.
Brawling magic: The only important spell in this tree that you should max out to level three is Rage though Ram may also be useful. This spell will come in handy with certain bosses when our gauntlet is not effective enough in dealing damage. You should only use it when you can get an opening for an attack. This tree focuses on doing as much damage as possible to your enemies and not worrying about how much they do to you.
Deception magic: The only worthwhile spell from this tree that I can think of is Stab. It attacks enemies and bosses from a distance which is not bad to have. Mimic and Shift have their uses I assume. This tree focuses more of on finishing battles quickly and stealthily.
Solace magic: All spells in this tree will be important and all of the spells should be maxed out. The Prayer spell can be found in all trees and creates a motionless clone of Harkyn that attracts enemies and bosses towards it. The only difference is that it also provide a regen when you are near it depending on the Prayer spell used. For Brawling: health regen, for Deception: stamina/energy regen, and for Solace: mana regen. The prayer from soalce will be the most important one for our caster build. Prayer should be used mainly when fighting bosses and certain enemies to distract them while you attack them from behind or blast them with your gauntlet.
Shelter is an excellent spell that increases all of your defense, heals you over time, and has a thorns effect on enemies that attack you. When an enemy attacks you while this is up, they will get dealt a certain amount of damage that seems to factor in the amount dealt to you. This will also come in handy when you wish to conserve your health potions or are on a low supply.
Daze is another nice defensive spell. It creates a clone of Harkyn that slows down time on all who approach it. This allows you to attack slowed enemies with ease and it also reduces their defenses as well which increases your damage. Best to use against quick enemies or if you are fighting 2 or three enemies at a time. When the game first came out this used to work on bosses, but has since been fixed in a patch.
Punishment is the final spell in the solace tree and another good one. It creates an aura around Harkyn that occasionally stuns enemies and reflects the damage they would deal to you back onto them when they attack you. This works even while blocking. While they are stunned, you can get in a free attack with your hammer or gauntlet. This spell does not work on bosses to my knowledge.
The Solace tree focuses entirely on increasing defense, healing, and weakening enemies to make it easier for you to kill them.
For armor you will be using medium armor. Medium armor has more defense than light armor but less speed, and less defense than heavy armor but more speed. The best medium armor in the game is the Effect armor set as it has the highest defense of all medium armor sets. Though the Last Traitor armor set does increase spell damage by +30%.
Shields you will not be using as much and mostly will be blocking with your gauntlet and dodging, but focus on using the crest shield or heavy shield if need be.
For weapons you will be using hammers with faith scaling and requirements the most. The strongest hammer with faith requirement and scaling is the Stare hammer and the second strongest is Fly and make sure you equip them with flawless luck runes or flawless poison runes for poison DoT for some bosses. For Staff the only faith based one is Qamar which does fire damage. These weapons are the only ones you will be using as the others have strength or agility requirements.
As for Trinkets, the best one is the Faithful Disciple as it greatly increases your magic regen.
For your Gauntlet, you will want to equip the projectile with a Flawless power rune as that will make your gauntlet capable of killing most enemies in 2-3 cast and for some only 1. The explosive should be equipped with a Flawless magic run as the grenade constantly shoots at nearby enemies till it disappears. As for the blast, you can put whatever rune you like into that as you will not be getting close to enemies often to use it.
You will focus largely on using your gauntlet through out the game once your acquire it. You should only use your melee weapon when fighting most bosses and if an enemy gets too close for you to use your gauntlet. For most battles with regular enemies the only spells you will be using will be shelter, daze, and punishment. When fighting bosses, prayer and shelter will be your best spells.