I tend to buy XL shirts most of the time, and 2XL if it's made of material that can shrink. In this case, I bought a 2XL, and I was not disappointed with the length or width of the shirt itself. The material is light and fairly comfortable, but it is somewhat thin.
The design itself is very nice— a great nod to both the Hollow Knight as a character and to the game itself. It also comes with a sticker showing the Knight in the same pose as on the shirt. I have not yet tested how it holds up after a machine wash.
When I put the shirt on, I was confused at the sleeve length. I compared them to the lengths of all my other 2XL shirts, and the sleeves are about 9 inches shorter. They go about 6 inches past my elbows, making it feel very awkward and goofy. This is before any shrinking that may or may not happen in the washer and dryer.
Now that I look specifically for the information, it is stated in the description that it's a 3/4 sleeve shirt. I should have looked more carefully before I bought it, assuming that it was a long-sleeve.
I don't know how common it is for men's shirts to be in 3/4-sleeve, but I never knew that was a thing until today. Maybe I'm an exception, but looking at the images made me think it was a long sleeve shirt. I would suggest putting more obvious indication on the merchandise images that it is not long-sleeved, so that ignorant people like me don't end up getting confused when they don't get what they thought they purchased.