A Frostbolt Cast On Crit Comet Oracle for the Druid class unleashes a volley of Frostbolts exploding across the battlefield and freezing everything in sight. Comets automatically fall down from the sky whenever you deal critical strikes, dealing massive amounts of damage.
Normally Frostbolt pierces through all enemies only dealing damage once, but thanks to the Snakepit, (equipped in your left ring slot) it no longer pierces but forks instead splitting into 2 projectiles on hitting the enemy. This way Frostbolt detonates after forking, dealing damage in the area. Explosions from multiple projectiles can overlap damaging enemies many times which results in an amazing clear while mapping.
Use Frost Wall to create Ice Crystals, then destroy them with Frostbolt to create a chain reaction of explosions.. This is a perfect scenario for Cast on Critical supported by the Comet spell to shine. You generate a ton of energy for the Cast on Critical Gem thanks to numerous hits and 100% Critical Strike chance, resulting in amazing single target damage.
Early on you play a life/energy shield hybrid build. This combination is much easier to gear rather than going pure life or energy shield and creates a solid defense. Later on you switch over to Chaos Inoculation to access a larger effective health pool and makes you immune to chaos damage and bleeding. This means you no longer need any chaos resistance on gear which makes gearing much easier.
Snakepit is the core item for this build. Before you obtain it, play with Ice Nova for clear and Frost Darts for single target damage. Both of these skills require Cold Infusions to deal more damage so generate them through Frost Bomb and Snap.