The core function of a unit's Size is to determine how much space they take up in a square. Battlefield squares can hold only 10 size points.

Size has various other effects, however.

• The attacker must be able to reach the part of their target that they are aiming for. Hitting their Head requires the attacker's Size plus the Length of their weapon to at least equal the target's Size. Hitting their Torso is easier (-1 to the needed total), and hitting their Arms is easier than that (-2).
  • While everything can be hit, hitting the Torso has a weight of 5, hitting the Head has a weight of 1, hitting the Arms has a weight of 2, and hitting the Legs also has a weight of 2; if the attacker's Size is at least 2 greater than the target's Size, however, the weight for Head hits becomes 2 and the weight for Leg hits becomes 1.
  • For mounted units, the Size of the mount is taken into consideration. If the mount's Size is 2 greater than the attacker's reach, only the mount can be hit; otherwise, the chance of hitting the mount is 30%, plus 10% times the mount's Size, minus 10% times the attacker's reach.
    • If the mount is humongous to their rider, there is an extra chance for the mount to be hit instead of the rider; 25% if the Size gap is 3, 50% if the Size gap is 4, and 75% if the Size gap is 5 or greater.
• In melee combat, an attacker that is larger than their target is harder to hold off, while an attacker that is smaller than their target is easier to hold off. The Size difference is factored into the attacker's Morale roll for brute-forcing through a repel attempt.
• Units of Size 6 or greater wield bigger versions of the weapons that units of Size 5 or smaller use; these are one point Longer, so they are better at repelling and have a longer reach.
• Some enemies have a Swallow attack; they can only use this on targets whose Size is less than half their own.

• When multiple units are in a square targeted by a missile, the target is randomly chosen, with each unit getting chances equal to their Size. A Size 6 unit is twice as likely to be shot as a Size 3 unit in the same square.
  • The "fullness" of the square also impacts the missile's accuracy; half of the Size points in the square are added to the missile's DRN roll for landing a hit.
  • The chance for mounts much larger than their riders to take hits for their riders also applies in missile combat; otherwise, mounts and their riders have an equal chance to be shot.

• Big-enough units can displace their allies in combat, nudging them out of the way and into adjacent squares if they wouldn't fit, at the cost of 1 point of Combat Speed for that round. The Size gap has to be 3 or greater. They can also crush rocks and other props in this way.
  • Units with the Trample ability will displace enemies instead, dealing a minimum of 1 damage to them in the process. The Size gap only has to be 1 or greater in this case, and the displacement drives out all enemy units in the square – unless they're killed, of course. The Size of the Trampler does not affect the chance of being smushed for additional damage– this is determined entirely by the target's Defence Skill without their Shield parry– but it does add to the smush damage. Note that Tramplers do not displace allies unless they're in a rout, since their displacing always does damage.
• When a mounted unit's mount dies, the rider (if they're still alive) falls off, taking damage partly determined by the Size difference. There are some exceptions, however, such as Chariots.
• Units set on fire (typically by Fire magic) take damage that scales off their Size, since bigger units have more surface area that can be burned. The damage is not open-ended; it's a roll with a maximum equal to the target's Size, divided by 2, and then rounded up.
• Units have an innate resistance to paralysis (something typically dealt by Astral magic) equal to their Size, which reduces its duration by that much. This is since they have bigger brains, or more nerves to try to make numb, or something.

• Most beings need to eat. By default, a living, sapient being consumes a number of Supplies each month equal to half their size, minus 1/2. If their Size is 1 or 2, they consume only 1/2 a unit of Supplies each month. If they're an Animal, their consumption is halved.
• You can script units to focus on large monsters (the game uses the term "monster" in place of units in various places), in which case they'll focus their best efforts on enemies of Size 7 or greater. If there are no enemies of Size 7 or greater, Size 6 enemies will be targeted instead.
• While units can be "hidden" on the strategic map by having larger quantities of other units in the same space, this is significantly tougher to do for units of Size 6 or greater; reports will tend to mention one "towering over the enemy army".