Hey there, folks.

My name is Chris, and I'm looking for some assistance to build a magic system for my homebrew world, from people who know the True20 system better than I.

For world building background reasons, the gods have quarantined the campaign world, locking something dangerous in, and locking other dangerous entities out. PC races have (for lack of a better term) a spiritual organ in the center of their foreheads, which used to serve as an interface with the gods. Over the last couple of generations, it has repurposed itself as a collector of magical energies.

Like in RuneQuest, most everybody can tap into their magic for simple effects. A mercenary could sharpen her sword, increase her speed, or heal some damage.

Because the energies are filtered through living beings, they take on the humours of the individual.

Choleric nodes encourage people to be enthusiastic, intuitive, ethical, spiritual. A character could tap a Choleric node for spells such as:
A spell to bind soul to body, allowing healing magic to work for several minutes after a mortal wound.
A spell to see natural or ghostly spirits

Melancholic nodes influence people to be somber, sensible, materialistic, historical. A character could tap a Melancholic node for spells such as:
a Vampiric form of Healing
Wisdom Boost
Analyze a Machine

Phlegmatic nodes encourage people to be calm, reasoning, logical, scholarly. A character could tap a Phlegmatic node for spells such as:
Magic Resistance
Constitution Boost
Intelligence Boost, to learn a language currently spoken in the vicinity

Sanguine, or vitriolic, nodes encourage people to be cheerful, artistic, sensual, spontaneous. A character could tap a Vitriolic node for spells such as:
A few rounds of Regenerative Healing
Dexterity Boost
Charisma Boost

More advanced spellcasters could create effects that use two or three nodes, either of the same type or a combination of types. Different traditions follow the suggestions in the Adept's Handbook: the related traditions of druids and shamans, the related disciplines of illusion and mental magic, artificer magic, and the banned studies of summoning and binding.

One feature of this magic system is that virtually all spells have a very limited range. Those that aren't Self or Touch spells are almost all Short Range (25' + 5'/level).

My idea is that the number of nodes a character has starts at about 4 at 1st level, and that number grows slowly, maybe 1 or 2 per level. Characters will start the campaign at about 4th level, and they'll top out around 8th. Adepts are better at magic, not because they have more nodes, but because they are more economical in their use. A warrior casting a speed boost uses 1d6 nodes. A beginning adept spends 1d4 for the same spell. An experienced wizard might use 1d3/2.

So, what questions should I be asking? How should I proceed? What stories does this system suggest to you?