I'm working on story lines right now, and while large story arcs are fun, RPGs are all about developing your character. And to develop a character, you need something to develop. Every RPG system has and attribute system. D&D uses Strength, Constitution, Dexterity, Intelligence, Wisdom, Charisma. The Fallout Franchise uses S.P.E.C.I.A.L.

I feel like doing something for a little different. Instead of a zillion attributes, I want to keep it down to a rock-paper-scissors system of three opposing domains, and then have what other systems manifest as individual attributes be an alchemy of those three. It looks like this:

Mind, Body, and Soul are three domains that have various ways of supporting and opposing one another. There are just three attributes that a character possesses: Constitution, Intelligence, and Mana. Other attributes are combinations (or antagonisms) of two more more of the core domains. Charisma requires Mind and Spirit. Perception requires Mind and Body. Magic requires a balance of all three. Each of the domains has an attribute for how developed the character is in that domain. It also has an "energy" that is charged and depleted by character actions.

So in one sense I'm slightly more complex than Either D&D (with 6 attributes) and Fallout (with 7 attributes), but technically I only have 3 "attributes" with 10 "abilities" that naturally fall out of their interaction.

Pure Attributes

Pure attributes are where players allocated new skill points when they level up.
Intelligencemind The footprint of one's soul in the intellectual plane. A person string in intelligence can understand complexity and solve problems.
Manasoul The footprint of one's soul on the mystical plane. A person strong in mana has the ability to sidestep reality.
Constitutionwill The footprint of one's soul on the physical plane. A person strong in will is resistent to disease and injury.

Alchemical Attributes

Alchemical attributes arise from the interaction of core attributes. A character that is developed in Mind and Soul improves in Perception and Wisdom. A character that is developed in Mind and Will improves in Charisma and Savvy. A character that is developed in Soul and Will improves in Luck and Dexterity.
Charisma+mind +willThe ability to communicate ideas and influence others
Dexterity+soul +willThe ability to make ideas reality and perform feats of physical prowess
Luck-mind +soul +willThe ability to manifest low probability in the character's favor
Magic+mind +soul +willThe ability to warp reality
Perception+mind +soulThe ability to pick up non-obvious information from the environment and beyond
Savvy+mind -soul +willThe ability to manipulate rules as well as resist deception
Wisdom+mind +soul -willThe ability to make mental connections between ideas and events

But here is a twist. There are some attributes that are in opposition:

WisdombodyStrong opinions cloud wisdom
LuckmindThe power of reason tries to eliminate the role of chance
SavvysoulSuperstition makes one pedantically abide by rules in the physical world

If you are wondering where Strength (from D&D and Fallout both) occurs, I don't treat that as a separate attribute. Checks of strength will be rolled into checks of either Constitution or Dexterity. It's partly down to the design of this RPG. There isn't a lot of combat, and given the technological setting, little need for characters to lift heavy objects.