Advanced Dungeons & Dragons Second Edition (2E) grouped classes into three “superclass categories”: warrior, priest and mage. This categorization was dropped in Dungeons & Dragons Third Edition (3E), replaced with a distinction between arcane magic, divine magic and everyone else. D&D 4E merged these concepts in the form of class power sources. From the 4E PHB, page 54:

Every class relies on a particular source of energy for the “fuel” that enables members of that class to use powers.

That quote certainly makes power sources sound like a foundational mechanic that 4E PCs are build upon. One of my initial reactions to hearing about power sources was that they were resource pools that could be tapped to perform certain abilities. Alas, such was not the case.

The reality is that power sources are little more than fluff. They serve the same purposes in 4E as the “superclass” categories of 2E, a way to group classes of a particular flavor. That’s a waste, in my opinion. There are several ways to expand the role of power sources without radically changing the mechanics of 4E

Feats similar to multiclass power-swap feats could allow a PC to take a power from another source. There would be one feat for each power source and classification of power (at-will, encounter, daily, and utility). An example feat might look like this:

ARCANE APPRENTICE
[Power Source At-Will]
Prerequisite: Int 13
Benefit: You can swap one at-will attack power you know for one at-will attack power of the same level or lower that has the Arcane keyword.

These feats might require additional prerequisites to balance them with the cost of the multiclass power-swap feat and the restriction of powers from a specific class. Or you could just chose to do away with classes all together.

Another way to use power sources as a mechanic in the game is to build monsters that have defense bonuses (or penalties) against powers from a particular source. The bonuses could be power-based or static. A resistance to Martial powers might grant a bonus to AC or Fortitude, while a vulnerability to Arcane power would incur a penalty to Reflex.

What do you think about developing power sources more as a mechanic in 4E?