Way of Dark
Quake - Shoot a projectile which hits for 1 heart of damage and slows movement for a short time.
Cast time: 0.35 seconds
A quick cast time and no cooldown make Quake a good choice not only for Round 4, but for the rest of the game as a secondary ability. Add to that a slow-effect and Quake is one of the most reliable ability choices in the game. Try to pair this ability up with an instant cast spell or passive effect. The only trouble with the Augerer is your naturally slow speed and a need to stop and cast.
Leads to: Siren or Oracle