Constitution (also known as Build and is shown as Con in game) in Fire Emblem is a representation of how big a character/unit is. Constitution is also affected by characters that usually have Mounts (Pegasus Knights, Cavaliers, etc.). Constitution determines which weapons units can carry without suffering a penalty to their Attack Speed in battle, as well as which other units they can rescue and capture.
Similar to Movement, this stat only increases with the use of an item or through class change, with the sole exception of Fire Emblem: Thracia 776, where both Build and Movement possess growths. The items Body Ring and Statue Frag can increase the Con stat by 2, just as the Boots and the Talisman increase Movement and Resistance by 2 respectively.
Constitution and Attack Speed
In Thracia 776 and the Game Boy Advance Fire Emblem games, Attack Speed is determined by taking the unit's Con and subtracting the weight of the weapon equipped. Negative numbers result in a penalty to Speed for the unit. It should be noted that positive numbers do not result in a bonus to attack speed.
Unlike later games, in Thracia 776, this formula doesn't apply to tome users who always take their tomes weight into account.
Thracia 776 Formula
In Thracia 776, the Baron Boss, Gustav has a constitution of 20. The weight of his Master Lance is 16 and the weight of his Thoron tome is 9. When attacking with a Master Lance, Gustav's con (20) will be subtracted by the Master Lance's weight (16) equaling 4. This means Gustav will have no speed penalties when using his Master Lance. However if Gustav uses his Thoron tome, his constitution will be not be taken into account and as a result he will take a 9 speed penalty when attacking with the Thunder magic.
In Fire Emblem: The Blazing Blade, Nino's Con is 3. The weight of a Fire tome is 4. Therefore Nino's Con (3) subtracted by Fire's weight (4) yields a result of -1. This in turns means that when Nino enters combat, she will suffer a penalty of 1 Speed.
- Note that Attack Speed penalties do not result in permanent subtraction from a character's stats.
Rescue Stat - Mounted vs. Nonmounted Units
In the case of non-mounted units, the Rescue, or Aid, stat is directly proportional to the Constitution of the unit in question. As the unit's Con rises, so does their Aid. This allows the unit to rescue heavier units. In the case of Mounted units, Aid and Con are inversely proportional. As Con rises, Aid is lowered. The unit loses the ability to rescue heavier units.
For a unit to rescue another, the rescuer's aid must be higher than the rescued unit's Constitution. Because of this large Con is both helpful, and harmful.
Judgement of units' constitution amounts and caps
Usually, the constitution of units is judged based on their gender, class, and sometimes age. For example, units such as myrmidons have low constitutions due to their frail states, so even if they have incredible speed, they may not be able to hit twice against an enemy unit if they wield a heavy sword like an Iron Blade. Alternatively, units such as Fighters have high constitutions, as they have a thick and muscled state, allowing them to use most axes with ease. Mounts have little effect on a unit's constitution, and only affect rescuing, as it is the rider who wields the weapons, not the mount. Because of that, Pegasus Knights can only fight using Slim Lances without severely inhibiting their high speed. In the GBA series, non-mounted units have a max constitution of 20, while mounted units have a max constitution of 25. Note that it is only possible to reach these caps by either excessive uses of Body Rings (causing massive amounts of gold to be paid at Secret Shops), or by using cheats on a unit's stats.
- A comment by the creator of Thracia 776, Shouzou Kaga, indicates one reason for the introduction of constitution was to reduce the speed penalties given to wielders of heavy Axe weaponry.