This Unit can attack both ground and air. It also can create a block field to stop the enemy offensive for a short time. Especially at narrow entrances this abiliy will be crucial. This can be imagined like the Statis Field of Arbiter at SC original. But of course there are some differences. For instance this ability can not used over an enemy unit. But the advantage of the Nullifier unit is its far earlier place in new tech tree relative to Arbiters’ place. That means the usage of this ability can be at the early ages of the game. As you can see from the screenshot below, the two block fields stop the enemy Zerglings easily, it is also used for protecting the probes from a sudden rush offense.