Homebrew: Ability Skills

[preteriteeggnog]

I was asked to post this stuff to get a wider review.

Idea
I’d like certain advantages and power abilities (see GURPS Powers for how to create powers) to be skills instead of
advantages like Magery spells. I call these Ability Skills. I got the basic idea for this from a 4chan post.
To create an Ability Skill first build the advantage as normal. For power abilities one would typically make the
ability an alternative ability of a certain level of the power talent. Next, make a new Power Skill for the advantage
just like in the (Skills for Everyone option in GURPS Powers.) If the advantage does not already require a skill roll
add the Required (Skill) Roll limitation for the new Power Skill specifically made for this advantage. If the advantage
already requires a skill or attribute roll modify the roll to use a new Power Skill specifically for it. Next combine the
power skill with the advantage ability that relies upon the power skill.
To make a roll to use the advantage at Stat+0 one would have to buy the cost of the advantage plus the cost of
the Hard power skill (which is 4.) When we combine the power skill with the advantage we want to make the costs
to reach a roll of Stat+0 the exact same as previously. Buying up a Very Hard skill roll to +0 costs 8 points which is
the same cost as buying up a Hard skill to +0 (4 points) and a 4 point advantage.
So we can convert any 4 point advantage that uses a Hard skill into a single Very Hard skill and have the same
point costs.
Note that for alternative abilities:
• A 4 point advantage must be an alternative ability of a 15 point or higher advantage.
• A 3 point advantage must be an alternative ability of a 15 point or higher advantage.
• A 2 point advantage must be an alternative ability of a 10 point or higher advantage.
• A 1 point advantage must be an alternative ability of a 5 point or higher advantage.

Examples

Goetia
The calling on upon the demonic for power. Theurgy (calling upon angels) and necromantia (calling upon spirits of
the dead) could be stated up in a similar way.

Vis
It is well known that demons like to acquire souls. What is less well-known is that one of the major uses of souls is
transforming them into vis, a magically powerful substance very useful for creating magic items and casting powerful
spells. The basic unit of vis is the soul which is equivalent to the amount of vis extractable from one average human
in one quick go (as opposed to over a very long and painful eternity in hell.) Demons are always willing to accept the
raw resource, live humans, instead of vis.
Advantage: Goetia Talent 0 [8]
You are in tune with the demonic and receive the benefits of Empathy when dealing with them. As well, you can
Channel demonic spirits.
Use of Empathy with demons gives 1 corruption point.
Channelling demons gives 1 corruption point.

Advantage: Goetia Talent [5/level]
This magical Talent adds its level to Ritual Magic (Goetia) and to skill rolls for Theurgy skills. This talent is not the
same as Magery and should not be confused with it. All Goetia skills are limited by the following power modifier:
Note that demons are jealous and may squabble and fight with other demons under your service. Summoning
more than one demon at a time is not advisable.
Many demons are scary and terrible in appearance and require a Fright Check when first summoned.
PM Goetia [-20%]:
• Corrupting [-20%]

Skill: Imp IQ/Very Hard
You know the rituals to channel and summon an imp, a specific class of cowardly and weak demons who are most
useful for scouting.
Once the imp has been summoned and an appropriate sacrifice has been given (a small bowl of pig blood) you
can ask it to perform one favour for you. At the end of the service you can bargain with it for a new task. You can
bargain with an imp for different tasks but results are not guaranteed and the imp may become angry with you and
attack.
These favours are:
• Serve you as a familiar for 30 days.

Manoeuvre Time: 1 hour
Prerequisite: Goetia Talent 1
Corruption: 0

Total [1]
• Alternative Ability (Goetia Talent 1) [1/5]
• Allies (imp, 50%) [1]
• Constantly [*4]
• Summonable [+100%]
• Conjuration [+0%]
• Takes Extra Time [-120%]
• Requires (Skill) Roll [-10%]
• PM Goetia [-20%]
Skill: Mage Devil IQ/Very Hard
You know the rituals to channel and summon a mage devil, a specific class of cowardly but magically powerful demons
who are most useful for learning arcane lore.
Once the mage devil has been summoned and an appropriate sacrifice has been given (1 soul of vis) you can ask
it to perform one favour for you. At the end of the service you can bargain with it for a new task. You can bargain
with a mage devil for different tasks but results are not guaranteed and the demon may become angry with you and
attack. Some research into Hidden Lore (Demonology) may be required to find out which specific mage devil needs to
be summoned to teach which specific piece of information. Some skills mage devils never teach: if you want to learn
Erotic Arts summon a Succubus.
These favours are:
• Tutor you for 30 days in a skill. If you have not learned the skill in 30 days you need to pay again or find a new
tutor.

Manoeuvre Time: 10 minutes
Prerequisite: Goetia Talent 2
Corruption: 2
Total [2]
• Alternative Ability (Goetia Talent 2) [1/5]
• Allies (mage devil, 100%) [5]
• Constantly [*4]
• Summonable [+100%]
• Conjuration [+0%]
• Takes Extra Time [-90%]
• Requires (Skill) Roll [-10%]
• Trigger (Rare, Illegal) [-60%]
• PM Goetia [-20%]

Astrology
Astrology is the ancient means of divining information from the stars.

Advantage: Astrology Talent [5/level]
This magical Talent adds its level to Soothsaying and to skill rolls for Astrology skills. This talent is not the same as
Magery and should not be confused with it. All Astrology skills are limited by the following power modifier:
PM Astrology [-5%]:
• Accessibility (must know date and star map of area of interest) [-5%]

Skill: Astrology IQ/Very Hard
Requires Specialization
Use astrological calculations to make predictions about one specific subject or skill of expertise. Take at least 10
minutes to make appropriate calculations that ask for the answer to one question. On a successful roll your question
is answered as if a completely reliable supernatural Contact with an effective skill of 21 tells you the answer.
Manoeuvre Time: 1 minute
Prerequisite: Astrology Talent 1
Total [1]
• Alternative Ability (Astrology Talent 1) [1/5]
• Contact (nonhazardous, quick, skill 21, supernatural, completely reliable) [15]
• Takes Extra Time 6 [-60%]
• Requires (Skill) Roll [-10%]
• PM Astrology [-5%]

[dataweaver]

You could also take a page from the Pyramid Alternate GURPS article, “from Skills to Advantages” — but run in reverse. That said, Advantages tend to be pricey in comparison to Skills; so your Ability Skills are going to tend to be low-level. This can be mitigated somewhat applying limitations to the Advantage, such as energy costs and increased activation time; but those cap at -80%, so you're still limited as to how much you can cram into an Ability Skill.

All that said, note my sig. I'm very much favor of Ability Skills; but I think trying to derive them from Advantages (in particular, from the point costs of Advantages) is a mistake. I'd much rather see an Ability Skills system built from the ground up independent of Advantages, except maybe using the latter as inspiration for the former.

[Refplace]

Another way is to take Abilities at Default and use Techniques to buy off the penalty. This is the model PK did for many of the powers in GURPS Psionics.
For a lot of powers its cheaper than the AA method.

You need an Empowerment Advantage, which I suppose could be just a Power Talent (really a place holder) like you describe. Or a default power.

For Divination you could have Oracle with Active for 30 points.
Another information power would be built as one of the following...
7 pt power at -2 Skill
15 pt power at -4 Skill
22 pt power at -6 Skill
30 pt power at -8 Skill

Each costs 3 FP to use and the penalty can be bought off with a Hard technique.
Additional abilities could be made using Temporary Enhancements, Extra Effort and taking an extra penalty for a power that is not similar to the base power.

Note that you cant use a real Power talent for the base power as you would lose the skill when trying the new ability.
So the final write up would include ...
Empowerment Advantage (Oracle, Ally with Summonable, Innate Attack, whatever).
Power Talent to boost your effective rolls.
Power skill and techniques for you signature abilities.