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d20 Modern System Reference Document



Two kinds of cybernetic attachments exist: replacements and enhancements.

Replacements: Replacements are prosthetic or artificial units intended to replace lost limbs and damaged organs. Common replacements provide no benefits other than duplicating the essential functions of their biological counterparts, and they present little strain on the beneficiary’s overall well-being. In appearance, a cybernetic replacement can be recognizably artificial or virtually indistinguishable from the real thing.

Enhancements: Enhancements bestow new abilities or improve the recipient in some fashion. Enhancements include skeletal reinforcement, subcutaneous communications hardware, and weapon mounts. Some enhancements have visible external components, while others are hidden beneath the skin. Enhancements put more of a drain on the body’s resources, and recipients frequently suffer debilitating physical or mental side effects.


Cybernetic attachments are complex instruments with both electrical and mechanical components. Consequently, a character must have the Craft Cybernetics feat to build a cybernetic attachment.

Repairing a damaged or nonfunctional cybernetic attachment requires 10 hours of work and a successful Repair check (DC 25). A character needs both an electrical tool kit and a mechanical tool kit to facilitate repairs. Without one or the another, a character takes a –4 penalty on the check; without both kits, the penalty increases to –8.


Installing or removing a cybernetic attachment, regardless of whether it’s a replacement or enhancement, requires a successful Treat Injury check. A character with the Cybernetic Surgery feat suffers no penalty on the check.

Removing a cybernetic attachment without proper surgery causes lasting physical trauma to the patient’s body, dealing 1d4 points of permanent Constitution drain.


Only living creatures can have cybernetic attachments. In addition, a living creature can have a maximum number of cybernetic attachments equal to 1 + the creature’s Constitution modifier (minimum 0).

A creature may have more cybernetic attachments installed on its body can it can bear. However, the creature gains 1 negative level per cybernetic attachment that exceeds its maximum allowed. For each negative level, the creature takes a –1 penalty on all skill checks and ability checks, attack rolls, and saving throws, and loses one effective level or Hit Die whenever level is used in a die roll or calculation. Further, a character with psionic powers loses the ability to manifest one power of the highest level she can manifest (player’s choice), while a character with spellcasting ability loses the ability to cast one spell of the highest level he can cast. This loss persists until the negative level is removed.

Negative levels caused by having too many cybernetic attachments remain until the offending attachments are removed.


Cybernetic attachments provide countless benefits to their recipients. For example, cybernetic eyes can bestow darkvision, improve the accuracy of the recipient’s ranged attacks, or emit pencil-thin laser beams. A cybernetic brain implant can improve the recipient’s response time in a crisis, protect against mind-influencing attacks, or increase the flow of adrenaline throughout the body. The possibilities of cybernetic technology are endless. Although the benefits make cybernetics very alluring, the drawbacks are equally discouraging:


A creature with one or more cybernetic attachments takes 50% more damage from any attack that deals electricity damage. This vulnerability to electricity can be offset by an anti-shock implant (see Cybernetic Enhancements, below).


Whenever a creature exceeds its maximum number of cybernetic attachments, it gains negative levels until the excess attachments are removed (see Number of Attachments, above).


External cybernetic attachments are subject to attacks as if they were objects worn by their recipients.


Massive damage wreaks havoc with cybernetic attachments. Whenever a creature with cybernetic attachments fails a Fortitude save against massive damage, the GM should roll percentile dice and consult Table: Massive Damage Effects to determine what happens.

Table: Massive Damage Effects

d% Roll Effect of Failed Fortitude Save
01–30 Normal Effect
31–60 Attachment Disabled
61–80 Normal Effect and Attachment Disabled
81–100 Attachment Damaged and Side Effect

Normal Effect: The character immediately drops to –1 hit points and is dying.

Attachment Disabled: One cybernetic attachment (determined randomly or chosen by the GM) ceases to function until repaired (see Construction and Repair, above). The character suffers the effects of the disability—as noted in the description of the cybernetic attachment— for as long as the attachment remains disabled.

Attachment Damaged: One cybernetic attachment (determined randomly or chosen by the GM) continues to function but develops an unpleasant side effect that persists until the attachment is repaired (see Construction and Repair, above).

Side Effect: The character suffers a debilitating side effect as the result of a damaged attachment. Various side effects are presented on Table: Side Effects.

Table: Side Effects

d% Roll Side Effect
01–08 Blurred Vision: Character suffers a 20% miss chance on all attacks.
09–17 Constant Trembling: Character takes a –2 penalty on Dexterity-based skill checks.
18–25 Cybernetic Rejection: Character suffers 1d4 points of Constitution damage per day.
26–34 Dizziness: Character takes a –1 penalty on attack rolls, saving throws, ability checks, and skill checks.
35–42 Impaired Hearing: Static distortion imposes a –2 penalty on all Listen checks.
43–50 Impaired Vision: Distorted images impose a –2 penalty on Spot checks.
51–59 Insomnia: Character can only sleep for minutes at a time and gains insufficient rest to heal naturally.
60–67 Muscle Cramps: Character moves at half speed.
68–76 Muscle Fatigue: Character takes a –2 penalty on Strength-based skill checks.
77–84 Power Surge: Character is shaken for 1 round if wounded; a successful Fortitude save (DC 12) negates.
85–93 Psychosis: Character suffers 1d4 points of Charisma damage per day, lapsing into a coma if the score drops to 0.
94–100 Sensory Overload: Character is stunned for 1 round if wounded; a successful Fortitude save (DC 15) negates.

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