Petal is a Meekos, which is a race of creatures that lives with and controls plants, gathering energy from sunlight. Their society is isolated but they seem to keep an eye on the outside world with the use of scouts. From what we can gather (heh) Petal is allowed to explore the outside world as a scout because she figured out how to channel sunlight offensively, making her munion pets explode then regrowing the seeds. She rides a Bramblethorn plant into battle, which is also where the munions sleep when they’re full.
Petal is collecting Halcyon shards (what her munions call glow-glow crystals) to bring back to her home and plant in the earth, to help the gardens grow. Her munions enjoy scouting the land, chomping enemies, and going “Boom, boom, boom.” They use their adventures to lord over the ents who remain in the Meekos’ land as guardians. After all, everyone knows ents are too stupid to do anything but stand guard!
While some fan theories allege that Petal is really a sinister necromancer feeding off the souls of her pets I think it’s fairly safe to say that’s she’s only in it to make compost out of her enemies and collect the shards for her home. And since the munions don’t seem to be upset at getting blown up (or farting, I’ve heard it both ways) there’s little reason to assume the worst of her. But what you think of Petal is up to you!