Frostbolt and Vortex are two new skills that'll be released with the 2.3.0 content update, and they introduce a new style of build to play in its challenge league. These cold skills can be used individually, but also have a unique interaction with each other.
The Frostbolt skill fires a slow moving, piercing projectile and is available very early in the game. It's good for taking on clustered groups of enemies, especially once you have access to the Lesser Multiple Projectiles support gem.
Frostbolt is an especially potent skill when used with the existing Ice Nova skill. Normally, Ice Nova releases a large, icy burst around the player. Now, if you've got a Frostbolt skill in flight, casting Ice Nova while targeting near a Frostbolt will cause the Nova to be cast from the Frostbolt's location, rather than the player's location. This lets you deploy Ice Nova's considerable area damage at long ranges, avoiding the dangers of close combat that Ice Nova usually puts you in.
Vortex is the second skill we're revealing today. When you cast Vortex, it releases a large burst of cold damage around the player and creates a chilling, damaging icy vortex. If cast while targeting near a Frostbolt, Vortex will destroy the Frostbolt projectile, performing the damage burst and creating the damaging vortex at the Frostbolt's location. This makes Frostbolt a great way to deploy multiple Vortexes across an area, without having to move to those locations.
Frostbolt can be used in combination with either Ice Nova, Vortex, or both! Here are the two new skills in action in the Waterways and Courtyard Maps.