I'm kinda confused on some of the themes. What do you mean by heroes, animals, and Ylisse and Pelgia?
For Heroes, there are a few different interpretations. We received a number of suggestions about the mobile game FE Heroes. You could write/draw a reunion scene, fighting with the other heroes, the family in different forms (Easter Chrom and Lucina, Summer Robin, Marth-Lucina), going to foreign lands to fight, etc. If you’re not into the Heroes video game, you could always do something about them being heroes in other ways, big or small - rescuing each other or others. (I’d imagine there’s some really cool superhero ideas to delve into!)
For Animals, it can be anything involving animals. In a modern AU, taking the kids to pick out a pet, or a dog-walking AU. Could also show Chrom trying to take care of his horse, or if you’re into angst, something could happen to their horses/mounts. You could do cat/bunny or other anthropomorphic ideas, these are really cute to see drawn out. And there’s also NSFW sexy times, “behaving like animals”. (We do accept NSFW submissions, as long as they are labeled as such!)
Ylisse and Plegia - we combined a few different suggestions for this one. Basically, you can explore the different styles of clothing and traditions that occur in the two very different countries. One suggestion that I liked in particular was “language barrier”. It would be really cool to see Chrom dressed in a Plegian outfit to combat the hot weather in Plegia, as an example. You could also do a Modern AU twist, Chrom and Robin exploring each other’s cultures and heritage, backpacking across “Plegia” or “Ylisse”… An Arranged Marriage AU could work really well with this prompt, too.
We tried to pick prompts that we haven’t done before, as well as prompts that can be interpreted a number of different ways. It is really about your interpretation of the prompt, and there’s no wrong way to answer it.
Please let us know if you have any other questions. I’m available to brainstorm if you want to come up with something to write/draw… I’m sarai377 on tumblr, and saraiwrites on twitter. I’m sure the other mods would be glad to work with you as well! Thanks for your question and I hope this helps!