What is an X?
The X's are a line of mutants from a hidden experiment in the Institute. The DNA is of two specimens of animals, 1.5% of the DNA of a specimen at one time, 3% of each specimen ONLY.
The Institute has kept the X's secret from even the School, only certain people know that we exist.
The X's are given gentle treatment until "The Test". The Institute was built over a jail, so instead of little crates, we have full-on jail cells. We can eat in a cafeteria, though it is heavily guarded and there is no way to escape, and we have time after meals to train with our groups.
Back to The Test. The Test is mainly a gladiator battle between the group and hundreds of Erasers to see which one is worthy to live. There are three rounds, sometimes they are all mashed together into one round, sometimes they are spread out. Two rounds are to kill off your teammates, one round is to see if you can live through the attacks of the remaining Erasers. If you die, you obviously lose. If you win, you begin to be treated like a regular mutant freak. You get normal tests for the other mutants, such as metabolic rate, stamina, taking blood and DNA, etc. to see how you survived.