OK. Chances are, you've seen the show "Avatar the last air-bender". If not, you can meander your way over to here and watch all the episodes for free (Don't worry. Its legal...) If you haven't seen this wonderfully wonderful show, then I'll explain it real fast:
There are four groups of people who can control the elements at will.
Fire, water, earth and air.
The fire nations king is trying to take over all four nations, and wipes out all the air-benders but Aang, who is the also Avatar and can bend all four elements. The avatars purpose is to keep peace in the world.
Throughout the story, Aang and his friends Katara, Sokka, and Toph (Later joined by Zuko) discover different variations of the main four elements. Some they discover on their own, others are closely guarded secrets that few know of.
Below is the chart of the elements along with the variations. The original elements already had symbols assigned, but I had to make up the symbols for the others. The chart is as follows:
Wait a minute- blanks? Ah yes. This is the purpose of the post. While there are 3 *main variations of the other elements, air only has one. Did the writers do this on purpose? Maybe. So what could the variations be? Methane?
Yeah. Methane works.
METHANE BENDING. OH BOY.
|Yeah. Methane Works.|
But that still leaves one square... Any ideas?
*There are some mixed variations, for example, mud; water AND earth.
PS Auto update! I'm writing this on Wednesday but it will be posted on exactly 12:00 on Friday. Yay!
EDIT: I stumbled across this. Interesting, and much better than mine, ha-ha.