Fera (previously known as Ira or Ferra) is one of the base metals from the alloy alignment system based on iron. It represents a gender that is, to some degree, partially unknown. It is similar to demigender and similar genders. One's gender is only partially known, or only partially defined by choice. The other part or one part is left ambiguous, either because it is unknown, or because it is left ambiguous by choice. What that known linity is, how strong it is, or how small it is doesn't matter. How one expresses or experiences their gender is defined by them. A fera person can have any alignment or presentation.
Fera was originally coin on December 1, 2018 by Hail, the original owner of the Tumblr blog lgbt-alchemy. At the time it is was called known as ira or ferra and the plural form was irum or ferron. On December 19, 2019 the alloy alignment system was reworked by Tired, the new owner of the blog. In this rework the name of the term was change to fera. The plural form would presumably be feron.
The flag is based on the color of iron. The symbol used is the symbol for Mars. It is the same as the male symbol, however this is entirely unrelated, as symbol was historically used to represent iron in alchemy. The reason iron was chosen is because of iron's ability to mix and become stronger with almost any metal.