Kill Void Baron Galaxis and collect his soul shard. Take the shard to Ogath the Mad in Spinebreaker Post.
My warp rift generator is complete. You can now use it to summon a true prince of the void, a creature whose soul shard will tell us much of what lies beyond.
Go south in Void Ridge and use my warp rift generator near the void stones. Look for a cluster of crystals near the edge of the abyss. A huge warp rift will form and Void Baron Galaxis will surely appear.
Destroy this creature and bring me his soul shard.