I am setting up this community wiki to develop explanations of standard magic systems. The idea is that in a question, you can link to a post here that explains the core ideas of the system in question, instead of repeating that information in every question.
So. First I think we should define a template of what needs to be documented for each system. Please post answers of your recommended template and we can merge/swap etc to get a standard single template. Once that is completed we can populate the standard template for each system.
Use cases might help us write the template, so here are some examples of systems we might want to write up. This question is not about these systems. This question is about a template that we could use to describe systems like these.
System 1: I can do cool stuff but it costs me
System Name: The Feedback System
This system allows a caster to trigger incredible skills but the energy required to accomplish the task comes from the caster's body. Conservation of energy is required.
System 1.5: I can do cool stuff but it costs someone or something
System Name: The Siphon System
The energy comes from the world around me, any living thing can provide the fuel I need to perform magic. Conservation of energy is required.
System 2: The elements are mine to command
System Name: The Elemental System
I can manipulate the elements but only within the rules of physics. I can create fire with my will power but oxygen must be consumed (for example).
System 3: BOW TO ME YOU PITIFUL MORTALS
System Name: The Deus Ex System
My power apparently knows no limits or the limits are ambiguous and vague and only apply as a story-telling constraint.
Note: I include this system mainly to point out that questions based on it will (in my mind) always be idea generation. This system should not be used to ask questions.