nineball seraph

The upgraded version of Nine-ball and final boss of Armored Core: Master of Arena, it can be distinguished from the standard Nine-ball by its orange highlights and trademark wing-like back thrusters.
It can be considered one the most, if not the most, famous mecha in the Armored Core series because of its history and the difficulty of its fights when it appears.

It is associated with Cirno from Touhou by fans for the same reasons as its standard version, being one of the strongest ACs and its association with the number 9.
Nineball=Cirno is commonly depicted with Nine-ball Seraph's color scheme and thrusters.

This tag implicates nineball (learn more).