Let's make some possiblities of adventures that could happen in RuneTerra.

For Example, The Kumugu and Plague jungle seems like alot happens in the trees that we dont know about. Like how Zyra obtained her body. Possible episode that could happen: Ezreal is leading a exploration group in either one of the jungles. They discover breath taking sites and dangerous creatures of sort. Much like how Rengar found Gnar. Then they discover a hidden secluded area with green life they have never seen before. Then they see a feminine figure walking they're way. They wonder if it's a native woman of the jungle. All curiosity until Ezreal is seeing one of his men getting eaten alive by a giant plant they fail to notice. His crew is getting attacked by carnivorous plants and the figure seems to be the source of it. Taking a closer look he realizes that she is not a human.

And idk. Make up alot of scenarios that could happen. I doubt that anyone we know off is aware of Zyra's presence. This would be Ezreal's first encounter. Same could go with Varus and Darius.