Your character
All characters have 5 main attributes: Strength, Intelligence, Wisdom, Dexterity and Constitution. All primary attributes can be trained up to 22 and all other attributes can be trained up to 18, check your class to find our which is your primary attribute. There are also some additional attributes like AC and Save vs Spell, Hitroll and Damroll, level and tier level explained below.
Strength
Strength is the primate attribute of the following classes: Warrior, Knight and Ranger. Strength effects the following: Damroll, Maximum weight that can be carried, Maximum weight weapons that can be wielded. Directly affects the damage of some skills, such as joust and bash.
Intelligence
Intelligence is the primate attribute of the following classes: Mage, Sage, Bard, Psionist and Necromancer. Intelligence effects the following: Mana gained per level, Practices gained per level, Mana regeneration rate, Damage done by spells (requires 23 int and above for extra damage) and Study Spells Increase rate.
Wisdom
Wisdom is the primate attribute of the following classes: Cleric, Druid and Priest. Wisdom effects the following: Practices gained per level (up to max of 22, or 25 for prime stat), Mana gained per level (only a little)
Dexterity
Dexterity is the primate attribute of the following classes: Assassin and Thief. Dexterity effects the following: Armor class, Hitroll, How many items you can carry, Critical hits on Thief and Asn skills with that ability.
Constitution
Constitution is the primate attribute of the following classes: Monk. Constitution effects the following: Health gained per level, Protection against disease / poison, Immunity to disease / poison, HP Regeneration Increase