1. Introduction

Priest is the supporting Character of this game.  Priest will always support in teamplay, let it be by Relics, by healing or dishing out some extra DPS. Priests Branch off into 2 different Classes: Inquisitor, The DPS or Saint, The supporter. I do want to note that there are many different kinds of Inquisitors and/ or Saints and you can fill that job in with the idea that you have. Priests are known for Poledancing, Buffing and Zapping away. The advantages that Poledancing and Buffing give, is that you are a Wanted class for Nesting and the one supportive thing that Sets Paladins and Priests apart is that Priests have a Secondary Healing skill namely Healing Relic. Priest also has good defense, hp and mp , Making them durable and possibly even tankers.

However, aside of those advantages,Priests also have weaknesses. They are Slow and have low Superarmour. A priest focussing on DPS will never have the same DPS that for instance a Damage Dealing class like Sorcerer or Archer has. So Overall there arent that many disadvantages.
(+) Pros:
  • Priest is a Support class of the game.
  • Priest has many Buffs and 2 good heal skills.
  • Priest has a very big MP mod, defense and magic defense. Decent HP stat, not as good as Paladin.
  • Priest is a very good choice of class in a long run nest because of its high survivability, good HP/MP Mods and supportability.
  • Priest's Smallscale offensive spells have a low cooldown, bigger ones like Bind Relic and Holyburst have a longer cooldown.
  • Priest has powerful buffs to increase Defense, Lightattack and Magic/ Physical attackpower making them a wanted party class.
  • Priest is known for Poledancing in PVP. They Protect members in their team with healing/cure relics. While annoying and harrassing the opponents with Lightning Poles, Lightning skills. They can even snatch a fair amount of kills this way.         
(-) Cons:
  • However, a Priest, being the slowest class in the game, are victims for every fast classes if you are not careful. You have to outsmart the speed of every opponent you have using your Poles, dodges and Bindings.
  • However, a Priest has lowest DPS compared to other classes. 
  • However, a Priest has a few to no evasion skills aside of Aerial Evasion and Sidestep. Block is not counted as an evade skill as you still take hits.
2. Skills
2.1. Cleric Skills
I decided that I will not enlist skills that are not usefull nor beneficial to the Priesthood.
Thus You won't find Paladin oriented skills here or things like Holy Kick.
Do keep this in mind.
Shield Blow - Strike your enemy hard using your shield. Not really usefull for a priest. I used it for a while because of the low cooldown but I prefer the other "Physical"one.
PVP - *
PVE - *

Block - Defend yourself using your shield. Increasing this skill's rank will increase the amount of attack you can block per 15 seconds duration (PVE) and 12 seconds duration (PVP). This makes you block any attack 100% for certain duration. A basic tanking skills for a Priest with reasonable cooldown. Good skill in both PVP but PVE, but beware, it can interupt your other skill when casting.
PVP - ****
PVE - ****

Lightning Strike - Bash your weapon upwards and send a lightning afterwards. Also does an okay damage for a basic skill. Not so good in PVE but useful in PVP as combo chainer. Has Low cooldown so is usefull when other more important skills are on CD.
PVP - **
PVE - **

Charge Bolt - Charges up your weapon with electricity and send it down in four directions. A very good skill in PVE as it can attack multiple enemies and big bosses. Mad usefull in PVP due the fact that it can hit your opponent 4 times on close range. Pesky Warrior's will think twice when coming close. This is also favorable in PVE as it can decrease your opponent's light resistance for.. WUT? 15%!? DO WANT.
PVP - ****
PVE - *****

Half Turn Kick - Kicks an opponent in a half turn.  This skill is not used much. The only time ever that it should be used is kicking opponents like Warrior and SM into stun @ Pvp
PVP- **
PVE- *

Holy Bolt - Creates a holy bolt to damage and bind enemies. A very good skill in PVE and PVP. PVE wise it hits nicely on the bigger bosses. IT also is a usefull skill for binding big groups of mobs together placing them right for things like Grandcross or Chargebolt. PVP it binds enemies while damaging so you can A) run away or B) start your combo/killing.
PVP- *****
PVE- *****

Heal-  Heals you and your opponents based on the % of  HP.  Heal heals a % of your Max hp for yourself and for allies it heals the from the max amount of HP they have. A Must for PVP and PVE. Max it naturally. Heal heals the opponent based on the amount of total HP you have + a little more. Very usefull in PVP for healing nice amounts of damage away, same for PVE.  The Cooldown is a little long sometimes so thats annoying.
PVP-****
PVE-****

Slidingstep- A dash in any direction you want. Usefull for PVE and PVP. Used for dodging attacks or simply moving forward faster. Must get skill. Makes this slow class move faster.
PVP-****
PVE-****

Aerial Evasion- Avoid Falling down by hitting key. Usefull for PVE and PVP.  Especially when locked in annoying flying combinations that you can't break without this. Think of SM's Tornado or Harpy's Tornado for example. Only downside is long cooldown.
PVP-****
PVE-****

Toughness-  Physical Defense increases by certain %. I'm not sure if this skill also works in PVP . Ofcourse a must get. Any damage reduction increases our Tankness and survivability. Must max.
PVP-*
PVE-****

Mental Mastery  - MP % Increases. Does not work for PVP. A Must to get for Lategame Dungeons. You're going to need alot of MP. The max Amount of MP also has an effect on the amount of MP you recover, The more MP-> The better your MP recovery.
PVP-*
PVE-****

Physical Mastery - HP % Increases. Does work for PVP. Increases your HP, a must get naturally.  Your HealSkill is based on the amount of HP that you have so further increasing your hp is better.
PVP-****
PVE-****

Mental Training - Increases MP Recovery. Not sure if this works for PVP. Increases MP recovery, needed for Longterm dungeoneering. You can't support your team if you're out of MP can you?
PVP-?
PVE-****


2.2. Priest Skills
Before listing the skills, I would like to add some informations. Priest has 4 skill trees. The left one is the Magical Skill Tree which is focuses more on doing magical damage and purely made for damage purporses. Inquisitors love this. The second tree is a small Giant AOE tree it holds 2 skills namely Grand Cross and Holy burst. They are Long CD but big and effective AOE's. The 3rd Tree is the Relic tree. It holds damaging , healing and supporting relics. The 4th Tree holds 2 buffs. An armor +% Buff and a damaging+% Buff. Alongside these 4 tree's , a few skills are scattered that all have their uses.

Lightning Bolt- Summons lightning in front of you, can hit multiple targets at once. Has a chance to electrocute. This is the first of the Proper damaging skills a Priest will obtain. This is a very usefull skill for Aoeing, electrocuting and generally just damaging. Has low cool down as well.
PVE- *****
PVP- *****
Mind Breaker- Attack during a dash.  Low Cooldown. Personally I use this more in PVP than PVE. It isnt really strong but it always helps to damage somewhat. Dashing+ Attacking at the same time has its benefits in time management thus might prove usefull. Pre-Req for Chain Lightning.
PVE- **
PVP-***
Chain Lightning- Damages and Electrocutes the Enemy, it can "Chain" Lightning to others.  When used on a Single Target this attack will hit 3 times. The reason why this skill is a must get, must use and hated skill is because of the area range it can be used in. It virtually can hit anything as long as its close enough. It doesnt need to be target it simply attacks. Plus added to this it automaticly gives the electrocuted status, eletrocuting the enemy every 5 seconds. The only downside is that Eletrocute doesn't seem to halt big bosses in PVE like the Pink Minotaur or the White/Black Bull.
PVP-*****
PVE-****
Detonate- Detonate/Explodes electrocuted enemies. God I love this skill. This is the one skill I have been waiting for every since lvl 24 Cap. If you can electrocute alot of monsters in a dungeon, or boss mobs this skill will go BOOM! Currently the highest I've hit with this skill is 7.6k uncritted on the Boss @ Overlord Keep on Abyss mode. This is also great for PVP. Cast a little chainlightning dodge your enemy's. Press Detonate bamn, they take 4.5k-5k Damage. Makes Relic hugging an even better strategy. I'm rating it a little less for PVE due to the fact that most monsters have died before getting detonated.
PVP-*****
PVE-****
Heaven's Judgement- Floats up and uses a huge and damaging electric AoE Field. This is the ultimate if you follow the line of the first Tree, The Inquisitor tree. While damaging you are Invincible for a small time frame while frying any opponent in your AoE field. A Must get skill for Priests following the Inquisitor Line. In PVE you can use this to damage a boss or big group of enemy's. In PVP its good for trapping+ Damaging an opponent in a high damaging current. Only downside is the Long Cooldown.
PVP-****
PVE-****
Wand Mastery- Increases Magic attack % When using wand. This skill is generally gotten by Saints that use Relics alot. Doesn't have its uses for the Lightning tree much, they are better off being increased by Light% Damage. The Skill is passive so it doesn't have any cooldown. Works for PVE and PVP and increases the damage a lightning relic does+ Healing relic heals.


PVP-****
PVE-*****


Blessing of Light- Increases Light%. This buff increases Light% Meaning it increases the damage on skills as Chainlightning and Lightning Bolt. What is also does for other party members , is increase their Light Resistance. This results into that they take less damage from Light Mobs and skills and also have a higher resistance to getitng electrocuted. Must get.
PVP-*****
PVE-*****
Grand Cross- A giant damaging Cross AoE. This Skill has its advantages and disadvantages. The Disadvantage is that its slow. The advantages are that it is good damage, a Giant AoE and can be shot off into any direction, this also means Vertically not just Horizontally. The CD is allright. PVE wise usefull for Clearing huge mobs and hitting Big Bosses alot. In PVP used for Pushing and Luring.
PVE-****
PVP-****
Holy Burst- Giant Aoe Field damaging enemies. For PVE this skill is God. Clears huge amounts of mobs very easily and the damage does not suck either. The only downside is that the CD is very high so you can't use it that often. The High CD is problematic for PVP where this skill does not see much of its use. I can imagine that in Tandem with Bindrelic/Holy bolt and this skill. Huge groups of People can get hurt badly.
PVE-****
PVP-***
Lightning Relic- Summon a sacred lightning object and the enemy who gets close to the sacred object will suffer lightning attacks. There is a chance to electrocute the enemy. Must have skill for saints. Gives a continual DPS and supports by harrassing enemies in PVP as well as PVE. Has a very Low cooldown. Sometimes you can even have 2 of these down. This can be used as an Aggro Pole/ Diversion from yourself. Monsters will attack the Relic instead of you.
PVE-*****
PVP-****
Healing Relic- Summon sacred recovering object to heal teammates nearby the sacred object. The secundary healing skill. This skill is focussed on your MATK and not your HP like Healskill. The only downside is that the cooldown can be a little tedious if your HP is ticking down faster then you'd like. Also works on Team mates.
PVP-****
PVE-****
Cure Relic- Summon sacred curing object to cure team mates and increase light damage nearby the sacred object. I love this skill. It takes off the obnoxious slowing debuffs and more. It also increases my Lightdamage making my Damage skyrocket even more. I see it more usefull in PVP then PVE for the sole fact that you will get hit with debuffs way more often in PVP then PVE. The cooldown is Mediocre.


PVP-****
PVE-***
Bind Relic- Summon the frontal sacred object to disable the nearby monsters to move. The ultimate skill of Binding. This is Holy Bolts bigger brother. Downside is that it only Binds and does not damage but..who cares! This skill is usefull for trapping in PVP and PVE.  I'm not giving this a 5/5 due to the horrendous cooldown it has.
PVP-****
PVE-****
Miracle Relic- Draw a light magical formation and cast it around. Attack enemies and heal allies along with the drop of the magical formation. The Mother of God of all Relics. The Ultimate for any Priest following the Saint line.  This skill does pretty much all of it. Only downside is the huge cooldown.. I dont see it as usefull for PVP as PVE due to the fact that its less spammable and the enemy can simply run away. Unlike the way it is with Heaven's Judgement.
PVP-***
PVE-****
Protection Shell- Increase surrounding teammates' physical defense.  Must have spell! Everyone will love you for it in PVE and PVP. You will take less damage making your survivability longer then without.
PVP-*****
PVE-*****
Striking -Increase nearby teammate's physical attack. Must have spell! Everyone will love you for it in PVE and PVP. You will love it yourself! We as priests don't have the best DPS in the game and this helps increase it.
PVP-*****
PVE-*****
Vengefull Wave- Launch common assault when being attacked to unleash divine power to slash the nearby enemy. I'd say this skill is useless. I've seen people use it in PVP to counter but I dont think its worth the SP. For the mainfact that it doesnt always work like its said. And you actually have to get hit and I prefer to dodge then getting hit.
PVE-*
PVP-**
First Aid- Have a chance to break out divine power when being attacked and the caster's HP will be restored to a certain proportion. This skill seems interesting at first but its quite poor. And it has the same issue as Vengefull wave, you have to get hit before this actually works. Might have its uses for PVP though.


PVE-*
PVP-**

3. Builds
Okay, down to builds! In this section, I will explain about some builds that I recommend the most. To be noted, some of these builds are taken from other foreign versions like DNCN, JP, etc.
3.1. The DPS Inquisitor Build

This build focusses heavily on the DPS side of Priest. They use the Left Skilltree to their utmost capabilities and also obtain the skill Heaven's Judgement. They Ditch the Relic tree side. They also have the minimum amount needed in buffs. Meaning Lvl 5 Lightbuff, Lvl 2 Shell and Lvl 3 Striking. This build is for the kind that like to be killing Machines and also great @ PvP. The only downside I can think of with this build is that you don't really fit the Criteria as DPS as well as a lets say Sorcerer would. And partywise you will get opted out over a saint due to not high enough buffs.
3.2. Hybrid Inquisitor

This type of Inquisitor Maintains their DPS status while putting in Minimal effort in the Relic tree up to the relic they want, let it be lightning relic + Healing relic or even up to Bind Relic. Hybrid Inquisitors try to have the best of both worlds. The minimum amount they have to spent in buffs is respectively Lvl 5 Lightbuff, lvl 2 Shell and Lvl 3 Striking. Their Damaging skills will have to suffer slightly to follow this build but are more effective in PVE then the Full DPS Inquisitor. In short Hybrid Inquisitor wants to be as supportive as a Saint but is more a DPS type of class.
3.3. Full Support Saint

This Relic Hugging tree totally ignores the Left DPS tree. They Put on the Pure focus for Relics, Buffs and Heals. They want whats best for the party and function amazingly in Party play. They are a little Poor in Soloing in comparison to Hybrid Saints. But hey, support class is support class, we aren't meant to solo! As you are the supportive type of Saint you have to work efficiently with your CD's because as soon as your Relics are on CD and you have buffed everyone, you don't really much else to do but dodge. This is the "Lazier"variant to the full potential of Saint. Because you Follow the Relic Tree your Ultimate will be Miracle Relic helping your party further in reaching their max Potential. Full Support Saints are not PVP material.
3.4. Hybrid Saint

Hybrid Saints are similar to Hybrid Inquisitors as they try to obtain the best of both worlds. Whereas Inquisitor Sacrifice Damage , Saints sacrifice a little on Buffs. They invest the minimum amount of SP in the Lightning Tree. Meaning that they put in enough points to unlock the next skill they want. The Reason why you see quite alot of Hybrid Saints is the pure fact that if you can't find a proper party, you could still Solo the Dungeon if needed. Another plus to Hybrid Saints is that they can work functionally in PVP unlike FS Saints. Because they do have some damaging and killing skills. In short Hybrid saint is a supportive Inquisitor Wannabe.
4. GEARS 

4.1. Potentials
Have Gears that are atleast +8. Remember that +10 Green=+8 Blue=+6 Epic.
It doesn't really matter . Potentials you should really look out for are Potentials that increase your magic attack by a % or your Light Attack by a %. Agi/Crit is always wanted and try to balance out your HP/MP using the potentials. Intellect potentials are also greatly appreciated. If you're going Saint Perfect stat usage would be INT/HP, INT/MATK in case of epics Agi is always appreciated but you mainly would want those stats. Inquisitors preferably want INT/AGI or Light/AGI . This boosting their critical rates and Damage.
4.2. Accessories (Rings, Necklace and Earring)

Aim for the best you can get. Preferably Rings/Necklace/Earring with an as high as possible Int bonus on them. There are Rings for Inquisitors that have a standard light % Bonus that helps increase their Lightning Skills. For potentials on Jewelry you should aim for having Int , Light and Magic attack %. Preferably Magic attack % on the Rings if you're going for Saint so that your Relics will do better damage.
Note: I would not recommend getting the cerberus set Jewelry because the regular Epics give better INT potentials and you could always craft int/Element boost or int/Matk on your equipments.
In my opinion you feel the most pain from Cerb set Jewelry on your rings. (Due to them giving Element+int or Matk+int potentials)
4.3. Suffixes
Although suffixes are not as important as the gears themselves, they are important. Many players want a proper suffix. There are so many to choose from so some people get confused. In this section, you can find the most suitable suffixes for your gears depending on your build. Okay, here we go.
Weapon
You might want these suffixes below on your weapons:
  1. Int: This suffix gives you extra damage at a certain %
  2. Fatal: This suffix gives you extra critical rate which is crucial for Critbuildpriests . All classes need critical rate yooo.
  3. Harsh: People always recommend this for the lulz. Gives bleed effect.
  4. Magical Destruction: This suffix increases your magic attack more. 
Armors 
As for armors, this all down to your preferences, seriously. My personal suffixes for my gears are mostly INT and Iron Wall to balance between MATK and HP, some use Luck builds for PVP but thats up to you. For PVE INT / Iron Wall is best. You could put Wind Heraldy if you're the critbuild Priest. As much INT as possible. If you're going Tankbuild/High HP priest , Vit Suffix is the way you can go as well.

5. Enhancement & Skill Heraldries
 
5.1. Enhancement Heraldries
 
Finally, the Heraldry. Heraldry is one factor that make Dragon Nest a unique game. With heraldry you can improve your character's ability and capabilities in terms of skill and stats. To do this, you need the corresporending heraldries and equip it in your heraldry slot. The heraldry window can be found by clicking the "Heraldry" tab below the Costume tab in your equipment below. Now, let me explain you the best heraldries you must get from Cleric - Priest- Saint/Inquisitor
In my Eyes the Enhancement Heraldies you should look out for are
  1. Wise Heraldy
  2. Magician's Heraldy
  3. Fatal Heraldy
  4. Vitality Heraldy
  5. Mp Regen Heraldy
  6. Shining Heraldy
  7. Tent Heraldy
  8. Wind Heraldy
  9. Health Heraldy
These are the Heraldies I have selected for my character. I could tell you what Heraldies you should get but I think everyone knows these things already but  I will elaborate the ones I have for now. You can experiment in your own way, this is only a guidance not a Rulebook.
  • Wise and Magician Heraldy increase your magical attack and Int. Even int grants a small magic attack bonus. 
  • Defense/Magic Defense Heraldy makes sure I survive long Enough in Nest in case I am forced to Tank( Cerberus anyone?) 
  • MP Regen is there for the long run. We have already experienced in Dungeons like Saint Haven that the Dungeons are Very long so having a worthwile MP bar+ MP recovery is worth your money and time. 
  • I have the Fatal Heraldy to increase my Critrate. 
  • Vitality is for the same reason I run Defense/Magic Defense Heraldy. Having a bonified HP stat makes sure you don't die fast and makes you durable in supporting your team. Thus having the Health heraldy increasing your Vit is also an added bonus!
  • Windplate does the same as Fatal plate only Windplate adds Agi and 4 Agi=1 Crit.. So keep that in mind for all you people who like a critbuild!
 
There are other heraldies you could check out like Para Resist or Stun Resist, but those are more PVP oriented. As I said...Think out/ Experiment what Heraldy settings you like as long as you atleast get Wise and Magician's Heraldy Because they are a must.
 
5.2. Skill Heraldies
 
For a Saint I have a  few Skillheraldy sets.
1) Lightning Relic CD, Heal CD, Healing Relic CD, Miracle Relic CD
2) Lightning Relic CD, Heal 3%, Healing relic CD, Miracle Relic CD
3) Heal CD, Healing Relic CD, Miracle CD, Optional
4) Heal 3%, Healing Relic CD, Miracle CD, Optional
 
Optional meaning you could get Bind/Cure relic CD...or Chargebolt + Damage/ Holyburst etc.
But Having Healing Relic CD/Miracle Relic Cd is pretty much a must.
Heal 3% or Heal CD is up to you.
 
Inquisitors should get
  1. Lightning Bolt Damage, Detonate Damage, Holy burst Damage,  Heaven's Judgement cd
  2. Lightning Relic CD, Healing Relic CD, Lightning bolt Damage, Heaven's Judgement CD 3) Heaven's Judgement CD, Lightning bolt Damage, Optional , Optional.

Heaven's judgement CD is a must, Lightning bolt damage is also a must.
The rest is optional. The first one listed is a pure DPS build. The second one is more suited for Hybrid Inquisitors.
But I think you get the point right? If not...Just ask me in the comments below.

Credit goes to http://forum.cherrycredits.com/forum/topics/view/morgestern-s-comprehensive-guide-on-priests