Mastering: this is a process of both power and respect. Mastering grants you the right of mastering the knowledge your path holds. Masters are granted spell, armors and equipment to use as you see fit: congratulations on mastering and may you study the path thoroughly.

Priest Requirements for Mastering

So you have reached 99, however there are several more obstacles one must overcome to be dubbed a Master. This first of these obstacles will be to train Ard Naomh Aite or Ard Ioc to max.

Priest Master Requirements
Ard Naomh Aite or Ard Ioc Maxed
Base: 3500hp/7500mp
Holy Ink + Holy Scroll = Holy Book
200 000 000 experience
Next you will require 200 Million experience that must be sacrificed to become a master. Once you reach 99 you will already have a good amount of this experience saved, so just hunt the rest until you reach 200M.

The base requirements for a Priest Master is 3500hp and 7500mp. Make sure you have this requirement before you continue. You may ascend to achieve this base, please look at the Ascension section of the site to find helpful ascending information.

Cthonic Remains
Creature Drops
Draco Sgail - Rogue Master Items
Ancient - Wizard Master Items
Old One - Monk Master Items
Draco Deathach - Warrior Master Items
Draco Avatar - Priest Master Item
Dhubh Seud - Nothing
All Draco's are found on Cthonic Remains 54, 55, and 56.
They all drop black stones at random.
--Thanks Explorer for the infromation.
Finally you will require two items that can be hunted in deep Cthonic Remains: Holy Ink and Holy Scroll. After you have achieved all these requirements you may start your Mastership.

Head to the Temple of Veil (choosing) and talk with the girl there: she will test your Mastership abilities.
Priest Master Equipment
Sacred Wimple
Sacred Mantle
Holy Hy-Brasyl Gnarl
Sacred Chief
Sacred Mantle
Holy Hy-Brasyl Gnarl
You will get to a point where she asks you to see the Suomi Fae Priestess to construct the Holy Book. Head to Suomi and she explains that you will require the Holy Ink and Holy Scroll to construct the book. If you already having these items, just speak with her again and she will give you the Holy Book. Return to the Temple of Veil and she will dub you a Master (after taking your experience).

You will notice that all your spells and skills now have a mastering ability of 100. You will also be given your Holy Hy-Brasyl Gnarl and Master Armor. For the stats on these items please check them out in the Priest Armor and Priest Weapon sections.

Finally you will also be given the spell "Mor Dion Comlha" which casts a Dion on your whole group. Right now you will want to head to Shinewood Forest 11 and speak with the Faerie there for your other master spell "Deo Searg Gar" and if you are pure you will receive "Deo Searg" as well. More information on these spells can be found in the Priest Spell section. Congratulations on Mastering!

Empowering and Enchanting your Staff

Now that you are a Master you may Empower (pure) or Enchant (sub) your Holy Hy-Brasyl Gnarl. To start this you need to talk with the Tagor Wizard. He will explain to you that you will need a Crux. So firstly you will need a Bent Crux and a Talos Ore which can be found in low level Chaos, creatures here will drop the ore and crux.

Once you get these go to the Abel Armorsmith and he will fix your Bent Crux into a Crux. After you have your Crux, return to the Tagor Wizard and he will replace your weapon: with an Empowered Version if you are a Pure Priest, or an Enchanted Version if you are subbed. Information about these weapons can be found in the Weapon section.
Empowering your Staff
Bent Crux + Talos Ore = Crux
Crux + Hy-Brasyl Gnarl = Empowered Gnarl(pure)
Crux + Hy-Brasyl Gnarl = Enchanted Gnarl(sub)

Master Equipment - Unknown Depths

You may also retrieved your Master Item from the Unknown Depths-Gem Ore Quest. For Priests you will receive Master Necklaces. You may get more information on this quest and the items in the Quest Section and Equipment Section of the web site.

Buying and Maxing Stats

Now that you are a master you may Buy stats. To do so go to the Temple of Choosing and speak with the attended. She will allow you to trade 150Hp points for one stat of your choice. You may repeat as long as you do not go over the Maximum allowed of that stat in your class, and you do not go under the Base Requirements for Health of your Mastership. For Priests your Max stats are: 100/180/215/150/100.