The god of Evolution with an optimistic worldview, Nila is one of the main characters of Portals of Phereon. Her special ability is that she can turn herself into other species she has had sex with, and by performing rituals she can gain skill points for permanent upgrades that affect every form or body parts for a special chimeric form. She can also adapt any character, giving them any genetic traits she has acquired in her trait library, or even learn to give them skills. While she doesn't have the same manner of customizing her units as Creation, or as many unique abilities as the Druid/Prince, Nila has incredible power and versatility. Depending on her form, she can fit almost any role and excel in it.
Her transformations give her more options in combat, but also other areas such as exploring and breeding, in contrast to the other MCs who get locked into specific roles as the game progresses. Unlike Creation, whose stats relies on genes to grow stronger; or Druid/Prince who needs to save then spend skill points gained; Nila gets a flat 5% boost with every level up which gives her a consistent power boost with every level. This make her easier to use early game, especially for new players.
All those options can be confusing, especially for new players. One way to play is to pick a role you want to stick to at the beginning, and hunt for related chimera parts. Transform regularly into slightly refined versions of that form while working on unlocking her special forms. From there, pick one that fits your playstyle, and transform whenever something updates your stats, like a level up or buying a skill tree perk. If you're ready for the complexities that all her options give you, it's time to look at party compositions.
Where party build-up is concerned Evo's first contribution is species versatility, since she has the ability to change her own genetic (inherited) species at the drop of a hat. The both expands your initial genetic pool of breeders and facilitates access to hybrids. The key advantage here is that you don't need to have access to recruiting a species to introduce that species gene through Evo - you can get some unavailable bases through the Arena, or though working at the Brothel. However this only applies to conventional Base Species and Hybrid Species. She can take on the forms of Impure Species but not their genes, so if you wish to breed those you'll have to acquire a breeding pair.
The second contribution is the fact that Evo can transform into a wide variety of forms, allowing for teams that the other MCs wouldn't be able to use as well, if at all. For example, shadow tiles buff shadow units while others get a debuff, making it better to compose your entire team around it. The other MCs can't stand in shadow without taking the debuff, but Evo can transform into something that takes advantage of it. This flexibility in team composition allows you to form parties for any situation. This is further enhanced by the HiddenPower perk that allows Evo to freely change the element and damage type of her units.
Finally, Evo can make the most of Uniques and gifted characters. Not only is she able to adapt a specific set of genetic Traits without the randomness of Mutagens, with her exclusive Adaptation Essence she can boost their stat growths as well, which the other MCs are unable to do.
In earlier versions of the game Evo functioned very differently from her current state, resulting in much more shapeshifting.
She would unlock base species and hybrids then level each form to increase her stats in related forms. Leveling as special forms gave increases to all stats across the board.
The perk tree was more a perk list which was much more open in terms of developing. Some options on the list could be acquired repeatedly, which provided a "post cap" growth avenue.
The total amount of possible leveling was extensive, with avenues for endless growth.
The newer perk tree has more trade-off perks and even perks that take more than give (like berserk).