Mechanics

Weapon Triangle
Like most Fire Emblem games, Warriors also has a weapon triangle where one weapon will be more effective against other weapons in a rock-paper-scissors fashion. The triangle is as follows:
 * Lances are strong against swords.
 * Axes are strong against lances.
 * Swords are strong against axes.

Having the advantage/disadvantage has various effects on combat as follows:

There are additional effects outside the Weapon Triangle which provide effective damage such as:
 * Bows are strong against flying mount units.
 * Specific type effective weapons (eg. Armorslayer vs. an Armored unit)

In-game, enemies are visually marked to show if they have a advantage or disadvantage with up and down arrows respectively.

Warrior Gauge
The Warrior Gauge fills up as a hero defeats enemies or collects yellow recovery items (Warrior Tonics). The gauge is visible in the UI as a yellow bar in the top-left corner.

Warrior Special
When one ore more bars of the Warrior Gauge are full, a Warrior Special can be activated.

Stun Gauge
During battle, a gauge may appear over an enemy. Attacking the enemy will decrease the stun gauge, and once fully depleted, a hero will deal a Critical Hit.