HP: Hitpoints; a unit dies when it's HP hits zero.
Strength: Strength + Weapon Might(Mt) - Defense = Damage dealt by your character to enemy.
Defense: Enemy Attack - Defense = Damage dealt to your character.
Magic: Magic + Weapon Might - Resistence = Damage dealt by your character to enemy.
Speed: Speed x 2 + Luck - Enemy Hit = % chance that Enemy attack hits your character. If your character has +4 speed then your enemy, your character will attack twice. If your character has -4 speed then your enemy, your enemy will attack twice.
Skill: Skill x 2 + Weapon Hit + (Luck / 2) - Enemy Avoid = % chance that your character's attack hits.
Resistence: Enemy Magic Attack - Resistence = Damage dealt to your character.
Luck: Enemy base critical - Luck = Enemy Critical. Luck also adds one point of avoid and hit.
Constitution: A unit can only rescue units with a lower Constitution then it's own rescue. If a character is using a weapon whose weapon weight is greater than it's Constitution, your character's speed will become Speed - (Weapon Weight - Constitution) = Speed. Example: Your Fiora has 9 Constitution and is wielding a Steel Lance with a weapon weight of 13, Fiora will lose seven point of speed and because of that, fourteen points of avoid.
Critical: Skill/2 + Weapon Critical Boost + Class Critical Boost + Mastery Boost - Enemy Luck. A Weapon Critical boost is the boost to your character's critical when equipped. For example: Florina starts with a Slim Lance. Slim Lance's critical is 5, so her critical becomes Skill/2 + 5 - Enemy Luck. Class Critical Boost is the boost that certain classes get for just being that class. The only classes that gain a Class Critical Boost are Swordmasters and Berserkers. They both recieve a 15% Class Critical Boost. A Mastery Boost is a boost that your character gets when they get an "S" Weapon Level.
When your character has a Weapon equipped that bests an enemy weapon, they recieve a +15 hit, +15 avoid, +1 might, +1 defense (or Resistence if your enemy is attacking with Magic).
When a character is in a Forest, they recieve a +20 Avoid and +1 Defense boost. When in a Fortress, they recieve a +20 Avoid and +2 Defense as well as recieving a % Heal when the Player Phase begins. When on a Gate of Throne, a character recieves +20 Avoid, +2 Defense, and +3 Resistence. Peaks award a character with +40 Avoid and +1 Defense. A character that is on Water recieves a +10 Avoid and a character on Sand recieves a +5 Avoid.
The better the Weapon, the higher Weapon Level required the wield it. Weapon Levels go in the order of E - D - C - B - A - S. If your character's Weapon Level is C, they can use all weapons C and below. If your chacter's Weapon level is S, they can use ALL weapons of that kind. To increase your weapon level, ?simply use a weapon over and over again.
Before promoting a character, wait until your character is level 20! This gives them an additional ten levels, which result in higher stats before promotion.