Ember Knights is a Roguelite in which players hack and slash their way to victory in a fast-paced environment. There is a free demo available on Steam for everyone if they want to see if they like the gameplay. You may have missed it if you aren't usually looking for demos on Steam.
Go to the Steam Page and scroll down slightly to find the demo. On the right side, above the game details (Single-player, Online Co-op, etc.), there is a button that says Download Demo. Most games will have their demos upfront and easy to see, so it's easy to miss.
Related: Does Ember Knights have multiplayer?
The demo only demonstrates the combat. The only thing you have to do is survive as long as possible using only a sword. While you cannot respawn and you cannot keep your loot, the gameplay is accurate to what the game will be like.
In addition to setting up the game and playing the demo, there isn't much else you can do. As soon as you start playing the demo, you can't go back to the main menu. The only way out is to quit the game.
For more games that offer rogue elements, why not check out our guide on When does Ember Knights go into Early Access? or Is Ember Knights a roguelike? Here on Pro Game Guides.