The void suppression crystal is an ancient xel'naga crystal, which can exude energy that slows enemy forces around it. In an alternate timeline where Zeratul survives the opening stages of the End War, he deployed these crystals against Amon's Forces.
The void suppression crystal is a calldown for Zeratul in Co-op Missions. It serves as an option after obtaining his first artifact fragment and reaching level 7. The crystal slows nearby enemy unit movement and attack speed by 70%, and disables all buildings in its radius. The crystal has a 30 second duration, and a 180 second cooldown. The crystal can be moved, and cannot be attacked.
Nearby enemy units have their movement and attack speed slowed by 70%. Nearby enemy structures are disabled.