Ciphers!
But, you know, not actually making one. If you somehow have one laying around feel free I guess.
But no, more like the concept of an MLP character dealing with one, be it using, decoding, maybe making a character whose talent is ciphers, et cetera.
You could have a fair bit of fun having somecreature discover a secret, that sort of thing.
Anyway, you’ve got 30 minutes to create followed by 15 minutes to submit! Have fun~