Enlargement is a magic effect that makes units big; one Size category larger, to be specific. It's generally applied by the Enlarge spell.

The Enlarge spell is a Level 2 Alteration that requires 2 and costs 20 Fatigue; or, if you're absolutely desperate, 1 and 1. It's a short-range "point buff" (an AOE-1 buffing spell) that applies the following effects for the remainder of the battle:

1. Size +1 ← If the unit is already Size 6, the spell fails to take effect!
2. HP +30% ← This increases both current and maximum HP!
3. Strength +3 ← This stacks with other Strength buffs, like Strength of Giants.
4. Defence -1 ← This simulates being a bigger target, or just not being used to bigness.
5. Map Move +2 ← This is never utilized in battles.
6. If the jump is from Size 3 to Size 4, the Weapon Length of non-intrinsic attacks is increased by 1.
7. Since Size determines projectile hits within your square, this increases your chance of being hit by them.

A maximum of six Size points can fill each square, but this spell doesn't cause units to displace each other; for example, three Size 2 Archers will remain in the same square when made Size 3, at least until they decide to move.

Enlargement has a couple of other sources, most of which involve the path of Nature:

1. Army of Giants is a Level 6 Alteration that requires 3 and costs 1; or, if you're desperate, 2 and 2. It has the same short range as Enlarge, but an AOE of 10; this means it can affect units further away, if the caster targets someone at the edge of their range.
2. The Larger Bless applies an Enlargement effect to all Sacred units, and is normally how you'll make use of that Map Movement bonus. It requires 43 on your Pretender, and is in effect even for Sacred units that aren't Blessed. It also applies to your Pretender, if they're Size 5 or smaller.
3. The Amulet of Giants is a Magic Item a 1 mage can make at Construction Level 4 with 5. It provides Enlargement while worn (even outside of battle), but only to units Size 3 or smaller. This kind of Enlargement stacks with other sources of it, but not with other Amulets of Giants.
4. Last-but-not-least, the Crown of the Titans is a Construction Level 6 Item that 21 mages can craft for 105, giving someone the regular variety of Enlargement along with some Leadership bonuses.

Enlargement has an effect that opposes it, of course, and that effect is Shrink. It has the exact-opposite effects of Enlargement, but is permanent; there is no way to permanently return a Shrunk unit back to their original size, and it can only be temporarily counteracted with Enlargement. On the bright side, Magic Resistance negates its application.

Two spells apply Shrink:

1. The Shrink spell is a Level 4 Alteration that requires 2 and costs 20 Fatigue; or, again, 1 and 1. It has twice the range of Enlarge, but that's still not a lot, though it does scale with overcasting. It also has an AOE of 1.
2. The Army of Rats spell is a Level 9 Alteration that requires 7 and costs 5; or, if you don't have that high of a level, 6 and 6. It Shrinks the entire enemy army, AND applies Battle Fright (an essentially-permanent 5-point Morale penalty) to everyone Shrunk. Only one MR check is made here; you either resist both effects, or you succumb to both.

There are also bad events in Laboratory-boasting provinces that can Shrink commanders.