Pressing F10 or alt freezes client.
 

If you press F10 or alt, your client freezes until you press the buttons again.

OS: Windows 7

This is not a bug though.

Oh, thanks for explaining my problems(?) I've been having.

You can also just press ESC or click on the game to fix it.

I've never really asked but in the Graal client, what is it that F10 is doing that causes this problem? Obviously ALT is allowing the user to open the title bar's context menu, but I'm pretty sure F10 doesn't behave like that by default.

I just think it is a freeze function for your screen. To hold a moment you want to screenshot or so. Doesnt look like a bug.

That seems like a decent function. People moving around when you have the right moment chosen can be a pain. I'm going with "Feature", too.

alt + 2 takes screens, f10 and alt alone don't need to. On player it can be abused pretty badly.

How can it be abused ?

Makes you appear lagged out aka you don't take damage and block until you unfreeze yourself.

If this is going where I think it's going, then I'm assuming that F10 and ALT are doing the old "ESC-Quit key prompt" trick that was often abused on servers like Era preventing damage being able to be received or some sort of craziness.

You can use it to freeze bullets on Era since the bullets are clientside.