XD:APEX is the codename for a Shadow Genesect. They are written by BittersweetNSour.
XD:APEX is not noted to be particularly different from any other known Genesect visually. They have been shown to use the High Speed Flight Form in a land-based "skittering", comparable to a Roomba, in order to draw less attention.
XD:APEX's personality is erratic. For the most part, they seem rather in control of their actions, being somewhat curious and inquisitive. However, they have somewhat of a hair-trigger temper, becoming enraged and going into Hyper Mode upon being denied information and being lied to. However, they can calm themself down unusually easily, pulling themself out of Hyper Mode after a single attack. They are very critical of their own temper, berating themself after recklessly attacking Eris.
Their speech patterns are likewise erratic. Primarily, they speak in slightly stilted Monese, enough to form full thoughts. However, they can also say short phrases in vocoded human speech, as well as utilizing audio excerpts from various media and pop culture in order to convey their thoughts. They can also respond in recordings of those they have spoken to.
In addition to the standard attack pool Genesect is known for, XD:APEX possesses a unique Shadow Move called Shadow Cannon. Its exact effect is unknown, due to having yet to hit its mark, but it was powerful enough to blast through a park bench without being impeded.
Based on XD:APEX's codename, they are implied to be part of the XD series of Shadow Pokemon following XD001, Shadow Lugia; as such, they are implied to be resistant (but not immune) to purification.