An Eira is one of the creatures available for Geneticist who have completed the mutation procedure from any of the base Homunculi.
Mostly a speed oriented Homunculus, with magic offensive skills that deal either Wind or Neutral property damage. Eira requires the consumption of Small Snow Flowers for feeding.
Eira and Geneticist Builds
Due to how Eira's Overed Boost works, VIT builds will be the most benefited from it while AGI builds will get the least of it. This is because the boost doesn't depend on the owner's stats. The ASPD given by Overed Boost has some advantages regardless of the Geneticist's build, like attacking Plant Mode foes (Emperium, Malaya Plants, etc.) and ASPD based skill delay. Some pros and cons may differ depending on which base Homunculus she mutated from.
Pros
Overed Boost can make Eira instantly hungry and can gain Intimacy faster, making some skills that "consume" Intimacy have some use (example: Self-Destruction from Vanilmirth)
Can use both Wind and Neutral property magic attacks, which basically can deal with all monsters.