What Did Snape Do In GoF?

[Alexander]

No: HPFGUIDX 34582

  Greetings!

  While re-reading PS/SS today, a thought has crossed my
mind. It is said in "Goblet of Fire", that Snape has done
smth for Dumbledore's case, possibly contacted Death Eaters
or else. But how could he do it?
  Voldemort knows *for sure* what side Snape is on. Remember
in PS/SS - Snape opposes Quirrell _directly_ and _openly_.
So there's no chance Voldemort can be left uninformed about
Snape. I would even suppose that Severus is #3 or #4 in VSL
(Voldemort's Slaying List).
  So the question is: what did Snape do? He couldn't contact
DE's - most likely they all already know how good Severus
is. Spy? No chance. It must be something not connected to
Death Eaters and Voldemort directly. Possibly finding
allies? Haven't the slightest idea.

Sincerely yours,
Alexander Lomski,
(Gryffindor/Slytherin crossbreed),
always happy to throw weird ideas into the community.