Level 1
Stabilized Rift: Hitting an enemy hero with Umbral Bolt through void rifts extend the duration of all active rifts by 3 seconds.
Blackened Zone: Void Zone radius increased by 25%
Embrace of the Void: Dark Tendril root duration increased by .5 seconds.
Level 4
Umbral Pierce: Umbral Bolt now hits up to 2 enemies if fired through void rifts.
Dark Refresh: Cooldown reduction from striking enemies in Void Zones increased to 1 second per spell. But removes the cooldown reduction from Void Zones damage over time
Darkness Spreads: Dark Tendrils root effect spreads to nearby enemies.
Level 7
Chaotic Void Energies: Umbral Bolt now slows enemies by 20% if they are standing in a Void Zone
What Lurks Beyond: Void Tentacles occasionally appear from active Void Rifts to attack enemies standing near them
Void Consumes All: Void Zones spread towards active Void Rifts
Level 13
Preternatural Calm: Active: Creates a shield around Umbric for 1.5 seconds that blocks the next stun, root, or silence effect. If Umbric blocks one of these effects, create a Void Zone around the enemy who cast it.
Chill of Night: Umbric gains 25 armor while standing in a Void Zone
Return to the Void: Active: Teleports Umbric to a selected Void Rift
Level 16
Void Transportation: Umbric can now teleport between Void Rifts.
Entropic Embrace: Striking an enemy hero with Umbral Bolt through a void rift grants Umbric 30% spell power for 4 seconds.
Spatial Rift: Can now have 3 void rifts active at once. Firing a spell into one now causes the 3rd rift to fire a clone of the spell as well.
Level 20
Void Desecration Orb: Void Orb now leaves Void Zones along its travel path.
Grasp of Telgorus: Shadow Grasp cooldown lowered by 15 seconds for each enemy hero pulled through the Void Rift
Umbral Rifts: Void Rifts fire Umbral Bolts at enemy heroes every 4 seconds. These bolts are empowered as if fired through a rift.
Tendrel of Darkest Night: Dark Tendril now pulls enemy heroes through the Void Rift.
Heroes of the Storm Build Guides
I have some complaints about the Void Rift implementation, but nothing big. First, you don't specify how long they last, or if they last until replaced. Second, it might be more interesting and skillful if you can quickly redeploy Void Rifts between abilities; it has a long cooldown and they could end up somewhere useless for a while if a teamfight moves location and Void Zone doesn't get enough hits. Also, Void Zone feels like it could use more interaction with the Void Rifts other than cooldown reduction; maybe if it's placed next to a rift it should move partway through the rift, placing some of its area on the other opening.
Anyhow, the concept is very interesting and looks like it'd be fun and tricky to play. There's also a lot of potential for talents with the Void Rift mechanic, so I look forward to that update!