Calculation damage is rather easy in Legends of Celestia. It is purely based on the attacker offensive power and the defender's defensive power, including any bonuses they might have. However, it is important to note that there are two damage calculations used. The following skills use a damage formula:
Arcana
Armament
Marksmanship
Spellblade
Minions gained using Dominion, Necromancy, and Summoning use the damage formulas as well, but the minions use their own statistics rather than the players. The damage formula remains the same, however.
Arcana
Damage = (((SpellStrength * (1 + (AttackerArcana / 100))) * (1 + (Augmentation / 100))) * ((100 - DefenderArcanaResistance) / 100))) + 1
Armament
Damage = (((WeaponStrength * (1 + (AttackerArmament / 200))) * (1 + (Augmentation / 100))) *( (100 - DefenderPhysicalResistance) / 100))) + 1
Marksmanship
Damage = ((((WeaponStrength * (1 + (AttackerArmament / 200))) + ArrowStrength) * (1 + (Augmentation / 100))) *( (100 - DefenderPhysicalResistance) / 100))) + 1
Spellblade
Damage = (((((SpellStrength * (1 + (AttackerArcana / 100))) * (1 + (Augmentation / 100))) * ((100 - DefenderArcanaResistance) / 100))) + 1) + (((WeaponStrength * (1 + (AttackerArmament / 200))) * (1 + (Augmentation / 100))) *( (100 - DefenderPhysicalResistance) / 100))) + 1)