Karthus's wall should act as a mobility interupting spell, and remove the slow.
Make it stop mobility and remove the slow from it. (Picture poppy's W but a line)
Make it stop mobility and remove the slow from it. (Picture poppy's W but a line)
On one hand, I'd like to have it stop dashes, but I wouldn't give up the slow to gain that.
Keep the slow (though maybe at a reduced amount), and then it's good.