This was a Free RPG day product for 2020, and specifically for this purpose 'Rain of Mercy' is a fast introduction to the basics of Wrath & Glory whole.
It gives you a quick taste of the baseline mechanics and characters (written much simpler than how they are in the full rules) while giving a basic adventure that has the hallmarks of a simple "grim" story with "dark" elements.
Obviously intended to be a Oneshot run in a day, I would find it hard to have the adventure last longer, which is the point as well. Allowing it to be a jumping point rather than something there to last.
[5 of 5 Stars!]