Invisibility

The ability to move about unseen is not foolproof. While they can’t be seen, invisible creatures can be heard, smelled, or felt.

Invisibility makes a creature undetectable by vision, including darkvision.

Invisibility does not, by itself, make a creature immune to critical hits, but it does make the creature immune to extra damage from being a ranger’s favored enemy and from sneak attacks.

A creature can generally notice the presence of an active invisible creature within 30 feet with a DC 20 Spot check. The observer gains a hunch that “something’s there” but can’t see it or target it accurately with an attack. A creature who is holding still is very hard to notice (DC 30). An inanimate object, an unliving creature holding still, or a completely immobile creature is even harder to spot (DC 40). It’s practically impossible (+20 DC) to pinpoint an invisible creature’s location with a Spot check, and even if a character succeeds on such a check, the invisible creature still benefits from total concealment (50% miss chance).

A creature can use hearing to find an invisible creature. A character can make a Listen check for this purpose as a free action each round. A Listen check result at least equal to the invisible creature’s Move Silently check result reveals its presence. (A creature with no ranks in Move Silently makes a Move Silently check as a Dexterity check to which an armor check penalty applies.) A successful check lets a character hear an invisible creature “over there somewhere.” It’s practically impossible to pinpoint the location of an invisible creature. A Listen check that beats the DC by 20 pinpoints the invisible creature’s location.

A creature can grope about to find an invisible creature. A character can make a touch attack with his hands or a weapon into two adjacent 5-foot squares using a standard action. If an invisible target is in the designated area, there is a 50% miss chance on the touch attack. If successful, the groping character deals no damage but has successfully pinpointed the invisible creature’s current location. (If the invisible creature moves, its location, obviously, is once again unknown.)

If an invisible creature strikes a character, the character struck still knows the location of the creature that struck him (until, of course, the invisible creature moves). The only exception is if the invisible creature has a reach greater than 5 feet. In this case, the struck character knows the general location of the creature but has not pinpointed the exact location.

If a character tries to attack an invisible creature whose location he has pinpointed, he attacks normally, but the invisible creature still benefits from full concealment (and thus a 50% miss chance). A particularly large and slow creature might get a smaller miss chance.

If a character tries to attack an invisible creature whose location he has not pinpointed, have the player choose the space where the character will direct the attack. If the invisible creature is there, conduct the attack normally. If the enemy’s not there, roll the miss chance as if it were there, don’t let the player see the result, and tell him that the character has missed. That way the player doesn’t know whether the attack missed because the enemy’s not there or because you successfully rolled the miss chance.

If an invisible character picks up a visible object, the object remains visible. One could coat an invisible object with flour to at least keep track of its position (until the flour fell off or blew away). An invisible creature can pick up a small visible item and hide it on his person (tucked in a pocket or behind a cloak) and render it effectively invisible.

Invisible creatures leave tracks. They can be tracked normally. Footprints in sand, mud, or other soft surfaces can give enemies clues to an invisible creature’s location.

An invisible creature in the water displaces water, revealing its location. The invisible creature, however, is still hard to see and benefits from concealment.

A creature with the scent ability can detect an invisible creature as it would a visible one.

A creature with the Blind-Fight feat has a better chance to hit an invisible creature. Roll the miss chance twice, and he misses only if both rolls indicate a miss. (Alternatively, make one 25% miss chance roll rather than two 50% miss chance rolls.)

A creature with blindsight can attack (and otherwise interact with) creatures regardless of invisibility.

An invisible burning torch still gives off light, as does an invisible object with a light spell (or similar spell) cast upon it.

Ethereal creatures are invisible. Since ethereal creatures are not materially present, Spot checks, Listen checks, Scent, Blind-Fight, and blindsight don’t help locate them. incorporeal creatures are often invisible. Scent, Blind-Fight, and blindsight don’t help creatures find or attack invisible, incorporeal creatures, but Spot checks and possibly Listen checks can help.

Invisible creatures cannot use gaze attacks.

Invisibility does not thwart detect spells.

Since some creatures can detect or even see invisible creatures, it is helpful to be able to hide even when invisible.

Overrun

It is not possible to Overrun as part of a charge. (Current editions of the PHB mention being able to do so, which really makes no sense.)

Source: 3.5 Edition PHB Errata

Bluff Synergy

Did you know that Bluff is the most synergistic (is that even a word?) of skills? It's true! Most skills only provide one or two synergies, but Bluff provides a whopping four, making it a handy skill for more than just Rogues.

Having 5 or more ranks in Bluff gives a +2 bonus on:
Diplomacy checks
Disguise checks to act in character
Intimidate checks
Sleight Of Hand checks

Light, One-Handed, and Two-Handed Melee Weapons

Did you know that you could use one-handed weapons in two hands to get the get the 1½ damage bonus from Strength? Read on!

Light, One-Handed, and Two-Handed Melee Weapons
This designation is a measure of how much effort it takes to wield a weapon in combat. It indicates whether a melee weapon, when wielded by a character of the weapon’s size category, is considered a light weapon, a one-handed weapon, or a two-handed weapon.

A light weapon is easier to use in one’s off hand than a one-handed weapon is, and it can be used while grappling. A light weapon is used in one hand. Add the wielder’s Strength bonus (if any) to damage rolls for melee attacks with a light weapon if it’s used in the primary hand, or one-half the wielder’s Strength bonus if it’s used in the off hand. Using two hands to wield a light weapon gives no advantage on damage; the Strength bonus applies as though the weapon were held in the wielder’s primary hand only.

An unarmed strike is always considered a light weapon.

A one-handed weapon can be used in either the primary hand or the off hand. Add the wielder’s Strength bonus to damage rolls for melee attacks with a one-handed weapon if it’s used in the primary hand, or ½ his or her Strength bonus if it’s used in the off hand. If a one-handed weapon is wielded with two hands during melee combat, add 1½ times the character’s Strength bonus to damage rolls.

Two hands are required to use a two-handed melee weapon effectively. Apply 1½ times the character’s Strength bonus to damage rolls for melee attacks with such a weapon.

Drawing or Sheathing Weapons

Drawing a weapon so that you can use it in combat, or putting it away so that you have a free hand, requires a move action. This action also applies to weapon-like objects carried in easy reach, such as wands. If your weapon or weapon-like object is stored in a pack or otherwise out of easy reach, treat this action as retrieving a stored item.

If you have a base attack bonus of +1 or higher, you may draw a weapon as a free action combined with a regular move. If you have the Two-Weapon Fighting feat, you can draw two light or one-handed weapons in the time it would normally take you to draw one.

Drawing ammunition for use with a ranged weapon (such as arrows, bolts, sling bullets, or shuriken) is a free action.

Strapping a shield to your arm to gain its shield bonus to your AC, or unstrapping and dropping a shield so you can use your shield hand for another purpose, requires a move action. If you have a base attack bonus of +1 or higher, you can ready or loose a shield as a free action combined with a regular move.

Dropping a carried (but not worn) shield is a free action.

Cover

The cover and line-of-site rules in 3.5 edition are pretty complex and confusing. Let's try to break it down so we won't have any more rules breakdowns in the middle of combat. :P

Cover

To determine whether your target has cover from your ranged attack, choose a corner of your square. If any line from this corner to any corner of the target’s square passes through a square or border that blocks line of effect or provides cover, or through a square occupied by a creature, the target has cover (+4 to AC). Note that this is separate from and stacks with the -4 penalty for shooting into a melee combat.

When making a melee attack against an adjacent target, your target has cover if any line from your square to the target’s square goes through a wall (including a low wall). When making a melee attack against a target that isn’t adjacent to you (such as with a reach weapon), use the rules for determining cover from ranged attacks.

A low obstacle (such as a wall no higher than half your height) provides cover, but only to creatures within 30 feet (6 squares) of it. The attacker can ignore the cover if he’s closer to the obstacle than his target.

You can’t execute an attack of opportunity against an opponent with cover relative to you.

Cover grants you a +2 bonus on Reflex saves against attacks that originate or burst out from a point on the other side of the cover from you. Note that spread effects can extend around corners and thus negate this cover bonus.

You can use cover to make a Hide check. Without cover, you usually need concealment to make a Hide check.

Creatures, even your enemies, can provide you with cover against ranged attacks, giving you a +4 bonus to AC. However, such soft cover provides no bonus on Reflex saves, nor does soft cover allow you to make a Hide check.

Any creature with a space larger than 5 feet (1 square) determines cover against melee attacks slightly differently than smaller creatures do. Such a creature can choose any square that it occupies to determine if an opponent has cover against its melee attacks. Similarly, when making a melee attack against such a creature, you can pick any of the squares it occupies to determine if it has cover against you.

If you don’t have line of effect to your target, he is considered to have total cover from you. You can’t make an attack against a target that has total cover.

In some cases, cover may provide a greater bonus to AC and Reflex saves. In such situations the normal cover bonuses to AC and Reflex saves can be doubled (to +8 and +4, respectively). A creature with this improved cover effectively gains improved evasion against any attack to which the Reflex save bonus applies. Furthermore, improved cover provides a +10 bonus on Hide checks.

Attack Actions

Certain maneuvers that combatants can perform are not standard actions, but are actual types of melee attacks. This means that if you get multiple attacks, you can make multiple attempts to grapple, disarm, trip, or sunder, or any combination of the above. You can also make these types of attacks when given an attack of opportunity.

This makes Improved Trip and Combat Reflexes an especially potent combination. Say an opponent tries to charge past you to attack your ally. As an attack of opportunity, you can trip your foe, preventing his charge, and allowing you an additional attack of opporunity on him (which you could then use to grapple, sunder, or disarm).

Source: 3.5 edition FAQ.

The Full Attack Action

If you get more than one attack per round (because your base attack bonus is high enough, because you fight with two weapons or a double weapon, or for some other special reason) you must use a full-round action to get your additional attacks. You do not need to specify the targets of your attacks ahead of time. You can see how the earlier attacks turn out before assigning the later ones.

The only movement you can take during a full attack is a 5-foot step. You may take the step before, after, or between your attacks.

If you get multiple attacks because your base attack bonus is high enough, you must make the attacks in order from highest bonus to lowest. If you are using two weapons, you can strike with either weapon first. If you are using a double weapon, you can strike with either part of the weapon first.

Deciding between an Attack or a Full Attack: After your first attack, you can decide to take a move action instead of making your remaining attacks, depending on how the first attack turns out. If you’ve already taken a 5-foot step, you can’t use your move action to move any distance, but you could still use a different kind of move action.

Traps

The subject came up recently due to the fact that our 5th-level rogue had zero ranks in Disable Device. Every party is going to run into a trap eventually, but even if you can't disarm a trap, you still have a few options.

Ranged Attack Traps -- Once a trap’s location is known, the obvious way to ruin it is to smash the mechanism -— assuming the mechanism can be accessed. Failing that, it’s possible to plug up the holes from which the projectiles emerge. Doing this prevents the trap from firing unless its ammunition does enough damage to break through the plugs.

Melee Attack Traps -- These devices can be thwarted by smashing the mechanism or blocking the weapons, as noted above. Alternatively, if a character studies the trap as it triggers, he might be able to time his dodges just right to avoid damage. A character who is doing nothing but studying a trap when it first goes off gains a +4 dodge bonus against its attacks if it is triggered again within the next minute.

Pits -- Disabling a pit trap generally ruins only the trapdoor, making it an uncovered pit. Filling in the pit or building a makeshift bridge across it is an application of manual labor, not the Disable Device skill. Characters can also neutralize any spikes at the bottom of a pit by attacking them -— they break just as daggers do.

Magic Traps -- Dispel magic helps here. A success on a caster level check against the level of the trap’s creator suppresses the trap for 1d4 rounds. This works only with a targeted dispel magic, not the area version (see the spell description).