This is a list of all the different kinds of modifiers in this game.
The d20 system has quite a few kinds of modifiers, and Phoenix adds a few of its own. Knowing the bonus types is important because with the exception of Dodge and Circumstance bonuses, they do not stack. The following list includes all modifier types in the Phoenix role-playing game.
The bonus or penalty attached to your ability scores are ability modifiers. They apply to various die rolls (attack, save, skill, etc.) and character stats (e.g., Defence, Knockback Threshold, etc.) according to the individual ability score descriptions.
The bonus you get to use one skill when you have more than 5 ranks in another, related skill. The bonus to a primary skill equals +2 for every 5 ranks you have to the secondary skill. Synergy Bonuses do stack with themselves.
Armour grants an armour bonus, and this bonus applies to your Defence score. Physical armour, the Armoured enhancement of Power Armour, and the power Natural Armour all grant an armour bonus. Armour bonuses do not stack with other armour bonuses. They do not apply against touch attacks. An armour bonus that is granted by a power or power-like effect does apply to touch attacks made by incorporeal creatures.
Awesome Bonuses are part of a linked set of optional rules under which the GM can decide that a player has done, or is about to do, something that is just so damn clever that the player deserves a bonus for even thinking of it. Awesome Bonuses can theoretically apply to any roll, but primarily apply to attacks or skill checks, which is to say, rolls that require a direct effort and/or some show of skill on the part of the PC.
Circumstance modifiers (bonuses or penalties) result from a specific conditional factor that impacts the success or failure of a task at hand. Circumstance bonuses stack with themselves as well as other bonuses.
[Attack, Save, Skill, Caster/Manifester Check]
Competence modifiers (bonuses or penalties) affect your ability to perform a particular task. They can apply to attack rolls, saving throw, skill checks, caster/manifester checks, or any other check that might normally be affected by your level or skill ranks. It cannot apply to ability checks, damage rolls, initiative checks, or any other rolls that aren’t related to level or skill ranks. Competence modifiers do not stack with themselves.
Cover bonuses affect your Defence score in situations in which something physically blocks an attack from striking you, such as a wall or tree, but they can also include “soft” cover such as a another combatant. Cover bonuses apply directly to your Defence under specific circumstances, and they are different from Concealment, which is a percentage-based miss chance granted by anything that makes you hard to see rather than hard to physically strike. For example, blindness, fog, or a sheet billowing in the breeze could all grant Concealment under the right circumstances.
Deflection bonuses are powered effects that make attacks rebound or veer away from the target harmlessly. They apply to your Defence score. Deflection bonuses do not stack with themselves. They do apply to touch attacks.
Dodge bonuses represent your ability to evade an attack entirely. They apply to your Defence score, and very occasionally to a Reflex save. Any situation or effect (other than wearing armour or other protective gear) that negates your Dexterity also negates a Dodge bonus, like being caught flat-footed, for example. Dodge bonuses do stack with themselves, and they apply to touch attacks.
[Ability Score, Attack, Damage, Defence]
Enhancement bonuses arise from powered effects only, so they always have an Origin. Enhancement bonuses do not stack with themselves. However, enhancement bonuses on protective gear (including armour or shields) effectively raise the bonus on the gear, so you can wear armour +2 and carry a shield +2 and both +2’s count towards your total Defence score. Enhancement bonuses count against touch attacks only if they enhance something that counts against touch attacks (e.g., a shield).
Equipment modifiers (bonuses or penalties) represent the aid that tools or machines grant in performing a certain task. They do not stack with themselves. They apply to skill checks, and very occasionally to saving throws.
Insight bonuses represent an instinct for a certain task that borders on precognition. Insight bonuses do not stack with themselves.
Luck modifiers (bonuses or penalties) represent a tendency to either benefit from, or be penalised by, random events. Luck modifiers do not stack with themselves.
[Attack, Defence, Skill]
Mastercraft bonuses result from the specialised modifications to tools, arms, and machines that increase their effectiveness. They usually represent things like superior materials or delicate weighting. Mastercraft items are either speciality brands or custom made. Mastercraft bonuses do not stack with themselves, and they count against touch attacks only if they enhance something that counts against touch attacks (e.g., a shield). They also do not stack with mods to Body Armour or Firearms, nor do they stack with Enhancement bonuses.
Morale modifiers (bonuses or penalties) result from greater than normal hope (or despair), courage (or cowardice), and determination (or apathy). Morale modifiers do not stack with themselves. Morale modifiers have no effect on non-intelligent creatures (those that have an Intelligence score of 0).
Natural Defence Bonus
Natural Defence bonuses result from the toughness or density of your hide. They apply to your Defence score. Natural Defence bonuses do not stack with themselves. Natural Defence bonuses do not apply against touch attacks.
Species modifiers (bonuses or penalties) result from a certain cultural context you were raised in and/or an innate characteristic of your physiology. Species modifiers do not stack with themselves.
Resistance bonuses affect your saving throws. Unless otherwise stated, they apply to all three saves. Resistance bonuses do not stack with themselves.
Shield bonuses result from carrying a shield or other item that blocks an opponent’s ability to harm you. They apply to your Defence score. Shield bonuses do not stack with themselves. Powered shield bonuses usually manifest as a barely visible but entirely tangible field of force that hovers in front of you. Shield bonuses do not apply against touch attacks.
[Attack, Defence, Grapple, Stealth, Various]
Size modifiers (bonuses or penalty) represent the logical consequences of being larger or smaller than Medium-sized. You can be only one size at any given time, so size modifiers can’t stack by nature.