I remember in some Dark Souls video there was some wizard (?) and he used some spell which looked like a sword slash made out of magic, it looked really badass, does any of you know what this spells name is and where to get it?

It's called soul greatsword and you get it in Drangleic Castle. Finally found after it continually wrecking me in pvp.

nevermind, it wasn't clear which game you were even talking about.

Is it any useful for meele characters as well?