You counter raum with your high sustain and cripple.
Tips:
Keep medium range
If Raum últs:
use obliterate or ult to counter
If he runs you can cripple him w/5stackDS
Dredge on paper would always beat you. Good thing he’s not a god. You can win by avoiding his shot and not missing... I know crazy but it just might work.
Cripple once he’s low and obliterate while in his ult to take no damage(if timed perfectly)