Crusader

Specialty Class

To become a Crusader, you must first become a Paladin. Once you have ascended to your new role, the Celestial Order will ask you to place a Crystal of Clarity within each of the three Shrines of Celestial Power. The first shrine can be found on the island in Lost Lake, the second among the Harrow Ruins west of Lake Dread, and the third within the Forbidden Lands south of Skuldoon (in the eastern deadend along the Southern Boulders border).
Once all three crystals have been placed, return to the Celestial Order to receive yet another quest. This time, you must travel to the Vale of Rune to defeat the Ancient Evil summoned by the wizard Volgar. Once you have confronted the foe, return to the Celestial Order to ascend into the Crusader class.

Learing Bonuses: Armor Skills, Basic Weapon Skills, Celestial Magic, Rune Magic, Shield Skills
New Skills: Crushing Blow
Stat Requirements: Strength 40, Intellect 40, Dexterity 35, Agility 30, Vitality 40, Honor 35
Skill Requirements: Heavy Weapons 10, Parry 10, Heavy Armor 7, Celestial Magic 10, Rune Magic 5

Installation: Dungeon Lords

For the original game (not the MMXII version), in order to earn advanced classes from base class onward, you will have to join one of four guilds in Dungeon Lords. When you join it, you’ll add the first tier adept class to your character (unless that was the class you selected at character creation). All four guilds work about the same. For each one, you’ll have to go on an initiation quest, then you’ll be given a second tier class quest, then you’ll be given a guild quest, and then you’ll be given a third tier class quest. You can join two guilds in the game, but you can only select one third tier class for your character, so try to plan out your advancement before selecting any quests.