What are the evolution stages in Aniimo?

Lumen is where most Aniimo start, the baby form you will be catching out in the field. Gamma is the middle: stronger, with new abilities, but not the end of the line. Nova is the one that matters most in combat, because Ultimate moves belong to final-form Nova creatures alone. A Gamma sitting at high level still cannot use one.

Evolving is generally worth doing. Most species gain higher stats and new abilities as they move up a stage, and anything you capture can be evolved, so catching something in its base form is not a wasted catch. Evolution is only one of the ways an Aniimo gets stronger, alongside standard leveling, traits, potential (Capability Points), resonance progression, carried equipment and runes, so a creature stuck at Lumen or Gamma is not finished growing.

Not every species has all three

Three stages is the full shape, not the guaranteed one. Some creatures have two. Some have none at all and stay in the form you caught them in. The majority of species can evolve, but if you are planning around Ultimate moves, check that the line you are raising actually reaches Nova before you invest in it. Lines are also specific: Flutternym evolves into Gracewing, and that is the path it has.

What evolving costs, and what skips it

Evolution takes specific resources, so it is not something that happens on its own when a level ticks over. Certain evolutions also want particular conditions or progression milestones met before they will trigger at all, beyond simply leveling the creature.

There is one shortcut. Catching an Alpha boss hands you an Aniimo that is already evolved, with none of the resource cost or milestone work. Starter transformations are a separate thing and do not count here. They give a temporary combat power boost and then wear off, so a transformed starter has not changed stage.

Not settled: The first stage turns up under two spellings, Lumin and Lumen. They refer to the same stage, so either one you search on is the base form.