- The status of the alternate versions: "past", "future", or "alternate".
- The origin of the X-Gene, and of the mutation generally, for clones, artificial mutants, etc.
The list is divided in three sections and spread out over two parts:
- The human mutants Homo sapiens superior:
- The non-Homo superior human mutants, including Homo supreme.
- The Non-Human Mutants, born from others forms of life, including aliens, robots and A.I.
The mutants who were powered before M-Day, dead or alive, known or not, and who were living and confirmed prior to the effects that the Avengers/X-Men war and the dispersion of the Phoenix had upon the mutant population.
Post-M-Day mutants known before M-Day
The mutants who were already powered and alive at the time of M-Day, and who haven't died and resurrected since, including:
- The 198 (the human mutants known by the American Government).
- The time- or reality-travelers who made their first steps in Earth-616 before M-Day.
- The pre-M-Day clones.
Mutants discovered/revealed after M-Day
Mutants who were activated before and were still active after M-Day, but were unknown before that event.
Mutants resurrected after M-Day
Include mutants dead, but powered at the time of M-Day, as well as characters alive after M-Day, deceased, then resurrected back, and also characters who were "recomposed", such as Nate Grey or Onslaught.
Mutants repowered after M-Day
Many mutants were repowered through various means after M-Day.
Post-M-Day new mutants
Mutants born or conceived after M-Day
A few mutants have born since M-Day, the most well known being Hope Summers, whose arrival relaunched the evolutionary process to break the M-Day effect. Other were conceived and known to be in gestation after M-Day but before the Avengers vs. X-Men war.
If there is a doubt, please classify the mutant as "activated after M-Day".