Attack rolls, damage rolls, defenses, skill checks, and ability checks are often modified by bonuses and penalties.
Bonuses: There’s one important rule for bonuses: Don’t add together bonuses of the same type to the same roll or score. If you have two bonuses of the same type that apply to the same roll or score, use the higher bonus.
An armor bonus is granted by your armor. The bonus applies as long as you wear the armor.
An enhancement bonus augments your attack rolls and damage rolls or your defenses. You gain an enhancement bonus to AC when wearing magic armor, an enhancement bonus to attack rolls and damage rolls when wielding a magic weapon or implement, and an enhancement bonus to Fortitude, Reflex, and Will when wearing a magic item that occupies the neck item slot (see page 249). You can benefit from a magic weapon, magic armor, and a magic cloak at the same time, since their enhancement bonuses add to different rolls or scores.
A feat bonus is granted by a feat. The bonus applies as long as you have the feat.
An item bonus is granted by certain magic items. The bonus applies as long as you wear the item.
A power bonus derives from a power or a class feature. Power bonuses are usually temporary or situational.
The proficiency bonus gained from proficiency with a weapon applies to attack rolls made using that weapon. You gain the proficiency bonus only when using powers that have the weapon keyword.
A racial bonus is granted by your race. An elf ’s Group Awareness trait, for example, grants non-elf allies within 5 squares a +1 racial bonus to Perception checks.
A shield bonus is granted by your shield. Shield bonuses apply to AC and Reflex defense. Powers, feats, or magic items might provide a shield bonus; these typically help only characters who aren’t using shields.
Some bonuses are untyped (“a +2 bonus”). Most of these are situational and add together with other bonus you have, including other untyped bonuses.
Penalties: Unlike bonuses, penalties don’t have types. Penalties add together, unless they’re from the same power. If two monsters attack you with the same power and each causes you to take a penalty to a particular roll or score, you don’t add the penalties together; you take the worst penalty.
A penalty might be effectively canceled by a bonus and vice versa. If you gain a +2 bonus to attack rolls and take a –2 penalty to attack rolls at the same time, you end up with a +0 modifier.
