The mechanics of Erfworld include:
The Hex Grid
The geography of Erfworld is laid out as a hexagonal-grid wargaming map, with each hexagon commonly called a "hex". Locations are described by non-cartesian X-Y coordinates (possibly designating a line of hexes and a specific hex within that line).
See the Movement page for a detailed examination of these rules.
The sides of a conflict alternate Turns, which is known as a Turn-Based Movement mechanic. For instance, in The Battle for Gobwin Knob, the sequence of turns is: Jillian's Turn (barbarians move first (Do they always? Let's find a source for this claim)), Transylvito's Turn, Charlescomm's Turn (early morning) Gobwin Knob's Turn (late morning), followed by the RCC's Turn (afternoon), followed by dusk, then nighttime and a return to morning. Alliances change the turn order (the turn of the alliance is that of the member which is last in the sequence), so Jillian is never seen moving except on RCC's or Transylvito's Turn.
Units may only move to another hex during their Side's Turn. Each unit has a specific amount of "Move" which determines how far it may travel during one turn. Units' Move is set to their maximum at the beginning of their side's Turn. At the end of the side's Turn, its units lose any unused Move, and may not leave their current hex until their side's next Turn. Exception: a unit with no remaining Move may leave its hex (on its Turn) by riding atop a Mount, or (on an enemy's Turn) by being captured and transported as a prisoner.
See the Unit page for more details on these rules.
Units are things that fight. Units may combine to form stacks or may fight alone.
Main Article: Stats
Unit Statistics are also known as "Unit Points"Erf-b1-p040. Statistics are numerical values that denote the ability of a Unit relative to other units with that same ability. In general, a higher value is better, but this may not be true in all cases. Every Unit has a minimum of six basic statistics. Depending on its Natural Abilities, it may have more.
Some Units have one or more natural abilities. Known examples include flight, fire, poison, and even the ability to cast some spells.
A unit with the Leadership ability is called a Warlord or Commander. A unit with magic-using ability is called a Caster (more commonly, it is referred to by its specialty, such as Croakamancer, Dirtamancer, etc). Warlords and Casters can see the stats of a unit directly; Lookamancers can determine the stats of units at a distance.
See the Combat page for more details on these rules.
Combat in Erfworld occurs inside a single hex or zone. A hex border will stop attacks like it does Movement.Erf-b1-p115 Movement inside a hex is unrestricted for both Sides, allowing maneuver warfare on a limited scale. Attacking is simultaneous for all Sides, which makes this a Real-Time Combat mechanic.
A Warlord (and sometimes Casters) provides a bonus to units under its command, as well as providing instructions and other benefits. Warlords also enable units in their stack to make directed attacks against specific enemy units, or to refrain from attacking at all.
Units in effective range of enemy Units may attack the enemy, and are sometimes forced to. The determination of which Unit kills its opponent is determined by the Combat Statistic, Defense Statistic, various bonuses (Stacking bonus, multiple Leadership bonuses, Dance Fighting bonus, Terrain bonus, etc.), and types of weapons being used by both sides. Damage can only be inflicted when the weapon is capable of reaching the opponent (ie. melee units cannot damage a flying unit with a ranged attack).
Defenders (Sides that are not on Turn) in Erfworld are limited in their activities. They cannot normally cast spells or Move out of the hex, although movement inside the hex is permitted. When a non-allied Side has Units in the same hex, the defender can reorganize stacks, attack, cast spells, and generally do anything it normally would on Turn if it were attacking.
As noted above, the time of day in Erfworld is related to the sequence of turns. The fact that the sun sets after Prince Ansom declares the end of his side's turn may imply that the turn cycle governs the time of day, rather than vice versa.
However, the link between turns and time is variable to some extent. At one point Stanley's turn is seen to start at dawn, rather than beginning later in the day, because there are no nearby units of any side that would act earlier. Later it is shown that Jillian of Faq is aware they will meet enemy forces because someone took a turn in the morning before they did. More than one Turn can happen simultaneously, as long as the involved Sides do not interact with each other.
Units can't walk off the hex when it's not their turn. They may, however, move within it, interact with each other and perform certain actions (such as taming wild creatures in the hex).
Non-Barbarian units without a side do not take turns, and are frozen in place (either inside their hex, or completely unaware of their surroundings) until captured or mercy-killed.
Each side has an area known as their battlespace, presumably defined as the hexes any of their units can see and/or reach. Units outside other battlespaces move at the start of the day, while those inside two or more battlespaces are bound by turn order.
A side's entire turn is taken at the same time: therefore, a single unit in another side's battlespace (unless captured or otherwise incapable of action) should bind that side's turn to the order.