Combat
Combat happens. When it does, you need to know what's going on, and more importantly, what your can do so as to not be raped, enslaved, or murdered. Firstly, here is a list of the basic things that a character can do on their turn.
-Make an attack using a weapon held in the character's hand.
-Make a grapple action against a creature that the character is currently grappling.
-Attempt to start a grapple with a creature that's within range.
-Cast a Spell.
-Use a Power.
-Draw a weapon or weapons (a character can hold one two handed weapon or two one handed weapons at a time.)
-Use a Succubus Power that requires a turn.
-Move in any unblocked direction up to 2x the character's Speed stat.
-Run in a straight line up to 4x the character's Speed stat.
-Full Defense: Defend yourself, giving up all other actions in exchange for a +30 bonus to Dodge and Resistance and a +15 bonus to Perception for that round.
-Sit there looking silly.
A few additional things:
-Movement: A character taking any of the above actions other than Full Defense, Charging and Double Movement can move up to their Speed stat in any unblocked direction or 2x their Speed in a straight line. In addition, drawing a weapon can be done in place of movement if the character is performing another action. Some special abilities allow creatures to substitute other actions for their move or don't allow them a move at all. Creatures using Full Defense can move up to 1/2 their Speed, and cannot run. A character's move action can sometimes be replaced by other actions, such as using a magic item.
-Defensive Fighting: Whenever a character would make any attack that requires an attack roll, they may fight defensively. Effectively, the character can sacrifice up to 20 points from their attack roll, gaining a bonus to Dodge for that turn equal to the number of points sacrificed. Characters may instead add the bonus to defensive fighting to their Perception or to their Resistance for the round, but this bonus only affects their Resistance when defending against effects, not for determining whether their own effects work. They may also trade their attack bonus to grant an adjacent creature a bonus to Dodge instead. In addition, they may forsake their ability to dodge all attacks directed at an adjacent ally for the round, taking any and all attacks that would hit that ally unless they come from a direction from which the character couldn't conceivably defend them. One can only move at 1/2 their speed while using Defensive Fighting, and cannot run.
Finally, characters with Activated Skills or Feats may use as many as they desire and meet the requirements for, so long as those Skills/Feats do not contradict one another in some way.
Attacks
Almost every attack, spell and power requires an attack roll. Those that don't have it indicated in their description somewhere. Attack rolls use the d20, and then add or subtract any appropriate modifiers. If the final number from the dice and all of the modifiers is equal to or greater than the Dodge value of the target, then the attack hits successfully and deals damage.
Area of Effect Attacks
Some powers, spells, and attacks hit multiple creatures within a given radius. The creature making the attack makes a single attack roll that is compared to every creature's Dodge score. Creatures that are in a grapple and lack the Brawler skill take full damage regardless of their Dodge score. Creatures with Brawler in a grapple and creatures not in a grapple who's Dodge score is greater than the attack roll takes 1/4 of the damage rolled for the attack, but creatures hit by the attack take full damage.
Grappling
Attempting to start a grapple works slightly differently than other attacks. When a character attempts to start a grapple, the GM rolls a d20 and adds the character's Grapple stat. This is treated as an attack therefore allowing the character to use Defensive Fighting, and the character gains any bonuses applied to attack rolls to this roll even if they do not increase the character's Grapple stat. If that total is equal to or greater than the target creature's Dodge stat, the grapple attempt is successful and both creature and character get the Grappled status. Whatever action the creature that became grappled was going to take can still be attempted if it's allowed by the grapple rules. If it isn't, then the action is lost.
Things work differently for characters in a grapple. When in a grapple, the character can attempt any of the following. When 2 characters are in a grapple, both declare their actions and then a d20 is rolled for both, and then add their Grapple stat to each roll. Whichever has the higher total gets to make their action, while the other character can take no action for that turn.
A list of options while in a grapple that require that the character win their grapple check:
-Penetrate (or be penetrated by) a creature.
-Perform foreplay on an opposing creature. If that creature is wearing armor that hasn't been shifted, the amount of pleasure dealt is decreased by the armor's DU.
-Attack a creature that you are grappling with using an unarmed strike, a directed spell or power, or a one handed weapon.
-Attack a creature that is not in the grapple. Taking this action also requires that the character make an attack roll to hit their target as well win the grapple check, and they take a -10 penalty to their attack roll.
-Shift aside the armor of one opposing character, allowing foreplay and penetration without penalty.
-Remove the armor of one opposing character. Characters attempting this action take a -4 penalty to their grapple check.
-Tear an opponent’s armor. If the character wins the grapple check, the opponent’s armor takes TP damage equal to the difference between the rolls. This damage ignores the armor's DU.
-Escape the grapple.
-Force a creature into a Submission Hold.
In addition, the following actions can be done without a check or using a turn while in a grapple.
-Shift your own armor.
-Remove your own armor. An opposing creature can attempt to prevent this, in which case this action becomes Escape Grapple.
-Release a creature that you are grappling with. An opposing creature can attempt to prevent this, in which case this action becomes Escape Grapple.
Also, the following can be done without making a grapple check, but if so, the character can take no other actions.
-Cast a spell. Direct spells like Bolt and Touch spells are treated as direct attacks, but AoE spells, buffs, utility spells, and summons require no grapple check to cast.
-Use a power. Direct attacks and AoE attacks work just like spells as above.
-Use a Succubus Power that requires a turn.
-Use Full Defense.
A character or creature who is within a Submission Hold cannot attempt any action except for escaping or those actions that explicitly say that they can be used while in a submission hold. The same rule applies to characters with the Bound status.
Group Grapples
When multiple creatures are in a grapple, generally it will be multiple weaker creatures trying to grapple one stronger one (multiple monsters trying to grab the same PC.)
In this case, each "side" is treated as a single monster capable of multiple actions. Each monster gets a single d20 roll, but they also get a bonus to that grapple roll equal to 1/2 the grapple modifier of the creature(s) grappling the same target.
If multiple monsters attempt the same thing for that turn, then the roll becomes 1d20 + the total grapple modifier of each of the creatures.
Finally, if multiple creatures that are not allied attempts to do something, each only rolls a grapple check against the target of their action for that round.
Creatures attempting to join a grapple make their attack roll against whichever creature has the lowest Dodge value.
Range Increments
Ranged weapons (not spells or powers) have a maximum range listed beside them. Characters can fire at targets beyond this maximum range, but take penalties to their attack roll depending on the range of the targets away from them.
Range Increments:
1x < C < 2x == - 4 penalty, 2x < C < 3x == -8 penalty, 3x < C < 4x == -16 penalty, 4x < C < 5x == -32 penalty, and you can't fire farther than 5x the range increment.
Where x = the weapon's listed range and C = the current distance to the target. The penalties would apply to attack rolls only.
In words: The character takes a -4 penalty to ranged attacks for the first range increment in distance to their target, and this penalty doubled for each additional range increment.
Ranged Weapons and Positioning
Characters using a ranged weapon can choose to orient themselves such that they gain a bonus to hit, but find it more difficult to move. Kneeling or crouching gives a character a +8 bonus to attack rolls with any ranged weapon except for thrown weapons, but the character must use a move equivalent action in order to take a knee and another one when they want to stand up. Characters using guns or crossbows may also voluntarily make themselves prone, giving them a +16 bonus to attack rolls but providing all of the penalties of the Prone status. Bows and thrown weapons cannot be easily used while Prone, and thus gain no bonus.
In addition, most ranged weapons are ill suited to use in close quarters combat. Using a ranged weapon when a hostile creature is within melee range of the character causes that character's attacks to take a -10 penalty to hit, and that character also takes a -10 penalty to Dodge.
Stealth Attacks made with ranged weapons don't automatically hit like melee sneak attacks do, and instead gain a +10 bonus to hit.
Clothing and Armor Damage
Normally, attacks deal damage to their target's TP equal to the damage that the character would have taken from the attack if they had no DR, Resistances, or AV, divided by the armor's DU. This only occurs if it makes sense given the nature of the attack, and sometimes character's or creatures may simply choose not to do it. A character may instead choose to attack the target's clothes only when attacking with a melee attack, and if they do so the target themselves takes no damage or other ill effects. The target's armor would take damage equal to the damage it would have taken if the character had been attacking the creature wearing the armor.
TP damage on armor doesn't automatically repair itself. It should be tracked like everything else in the status bar, and remains even after combat unless the character does something about it. Armor can be repaired given the time and materials, but for characters without the proper skill this can only restore an armor up to 1/2 their maximum TP. To fully restore a piece of armor, the character must take it to the merchant or to a competent smith/leatherworker/seamstress/etc and have it repaired there, at a cost equal to the max TP value of the armor to be repaired divided by 10, increased by 1 for every 100 denarii worth of modifications and enchantments made on the armor. So, an armor with 30 TP and 100 denarii worth of enchantments would cost 4 denarii to fully restore, for example.
Conditional/Prepared Actions
Rather than taking a normal action during their turn, the character can choose to prepare an action based on certain circumstances. For instance, a character could prepare to attack anyone that comes through a door, or cast a spell based on certain actions done by an NPC. Almost any action that can be done without conditions can be done conditionally. Some things, such as Sudden Shot and Counterspells, can only be used as prepared actions.
Positioning in Combat
Positioning in DG is abstracted rather than explicit, and so all positions will be in terms of relative distance and are decided largely by the GM when combat first starts, and then affected by the player's actions afterwards. Generally, distances will be given and then affected by character and creature movement. This may not always be precisely in line with the written actions, as attacks may cause explosions or push creatures in some direction without having any mechanical function that does that in the fluff. These are just for flavor.
More often than not, positioning and speed don't matter very much. Bonuses based on position, such as taking cover behind a wall when under attack from creatures using ranged weapons or attacking a creature from behind, are up to the GM to decide and aren't even necessarily consistent. There are times when positioning can matter, however, such as when a character tries to block access to a certain creature or attempts to step the flow of creatures through a choke point. In the former case, so long as the character is otherwise engaged (already being attacked or attacking something else,) they are realistically too distracted to actually do anything about the things moving past them, though the decision is ultimately up to the GM if they should allow such or not. In the latter case, the character should be able to hold the point unless they would reasonably displaced by an attack, at which point they'd no long block the point, though if the character misses with their attack and is hit by the attack of an opponent, it would be reasonable to say that they'd be pushed back as well. In other words, these sorts of situations should be handled however the GM feels is appropriate given the circumstances that create them, as the system wasn't built to have explicit rules for it.