Not all role-playing games are played on a monitor or TV screen. Some are played around a table with words and numbers, and when you're playing one of those, you're not limited to the monsters a developer has designed.
You're free to make your own. While this would normally be the domain of a role-playing game's Game Master, in this day and age imagination can sadly be a little lacking. Which is why we love Nicholas Cloister's "bestiary" of role-playing monsters so much.
It's a collection of original concept pieces for new RPG monsters, whose appearance and stats have been designed by former Game Master Cloister for use with your next evening of tabletop questing.
Useful then for D&D players, but you can also think of them as an elaborate new deck of Pokemon cards. Only, instead of fainting after battle, they deal 700 damage and devour your soul.
You can see the full "bestiary" at Nicholas' site below.