Sanderson's laws

So, there's this writer, Brandon Sanderson. He does a lot of worldbuilding. He's suggested three "laws" of Magic systems and characters, all three of which are somewhat /tg/ relevant if you're doing worldbuilding (in other words, homebrewing).

Sanderson's First Law of Magic

"An author's ability to solve conflict with magic is DIRECTLY PROPORTIONAL to how well the reader understands said magic."

In short, if the reader can't understand the solution to the problem presented, all you've done is just made a boring Deus Ex Machina. Unknown magic causing problems is perfectly fine, though, as is to a lesser extent preventing problems (not solving them, mind, but preventing from coming up (e.g., "We don't know how the magic keeps the water out of the undersea cave ruins, but that's fine as long as we don't have to examine it too closely.")).

• This statement applies to players, as well. If they can understand it, they can control it.
• You don't need to go too deep; the fact that the One Ring's effects are undone by destroying it, and that there's only one place on Middle-earth where it can be destroyed, are sufficient if the point is that the Ring is uncontrollable, and wants most of its wearers dead.

Sanderson's Second Law of Magic

"Limitations > Power" (For the purposes of reader interest)

Limitations are more interesting than powers. Almost nobody cares about a Superman story unless it either involves Kryptonite, magic, maintaining his secret identity, and/or his personal morality (all of which act as limitations on his power) or it features an at least roughly equally-powerful enemy (which usually revolve around the relative limitations of the two characters). Keeping this in mind is one of the best ways to avoid creating a Mary Sue.

• Elves are only fun if they're weak in some way or going against type.
• Part of what made the D&D Wizard so OP was that his main limitation was Spells per Day, which became less important as he went up in levels.

Sanderson's Third Law of Magic

"Expand on what you have already, before you add something new."

Less directly /tg/ relevant, but still good DMing advice. It's usually more interesting to the players to see some new aspect of an already understood thing (for example, a previously mentioned but mostly undefined part of town with understandable interactions with the rest of the town) than an entirely new thing.