Simple. Just write your favorite mythical creature and why you like it.
Don't be mean
Don't be rude
And don't include creatures that do anything bad or gory
Ok that's it
by mythical creature, I mean any creature that does not exist in real life, so you can even write down creatures that you made up yourselves. But if you do that, write what it looks like, what are it's behaviours, what it eats, etc. Etc.
My favorite mythical creature is a dragon cuz it is so epic!