The mechanics of Erfworld include:
The Hex Grid
The geography of Erfworld is laid out as a hexagonal-grid wargaming map, with each hexagon known in short as 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 confict 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), Transylvito's Turn, Charlie's Turn (early morning) Stanley'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, so Jillian is never seen moving except on RCC'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. 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.
See the Unit page for more details on these rules.
Every Unit has a minimum of six basic statistics. Depending on its Natural Abilities, it may have more (e.g. Leadership).
Move: A measure of a unit's ability to travel across the hex grid. Units have their move reset to its full value at the beginning of their side's turn; unused move reverts to zero at the end of the turn.
Experience: A measure of the amount of combat a Unit has participated in. This statistic increases as the Unit croaks enemies. The value of this statistic is hidden from other units and even from the Unit itself.
Loyalty: Although the result of Natural Thinkamancy, Loyalty is expressed as a unit statistic. However, the value any unit has is unknown. That value can be altered by Thinkamancy such as a Suggestion Spell.
Some units have one or more natural abilities. Known examples include flight, fire, regeneration, and poison.
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. (It is not yet known whether a hex border will stop attacks like it does Movement.) 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 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. (This may imply that more than one Turn can happen simultaneously, as long as the involved Sides do not interact with each other.)