Runes:
 
You'll find four runes hidden in the world of Quake.
Here's what they do: 

Elder Magic: 
Provides you with 150-250 points of energy and 
150 armor. 

Black Magic: 
Your attacks do 3x normal damage. 

Hell Magic: 
Reduces ammo usage. 

Earth Magic: 
Protects you from most damage, but won't save you
from quad attacks.