I changed Erupt somewhat on the testmap.
It does not cost energy, but each Eruptor has 2 charges with a 5 sec cooldown.
After the Erupt pushes units away it creates an area with lava that lasts for 10 seconds where the erupt hit. This area deals 20 explosive damage every second to any units (including the casters units) within it. It can no longer cast it while burrowed.
This is probably not an optimal spell, but here is the general idea:
Zerg has a couple of space control tools, such as lurkers and dark swarm (and lurkers + dark swarm ), but lurkers maaay be lacking a bit in controlling more open spaces and dark swarm is later tech. This ability is meant to be a weak supplement to lurkers, and can probably be used in other settings as well. Keep in mind that this ability is on a unit with a very different main purpose so it can't be too strong.
It would be optimal to have this ability also open up for some countermicro other than units moving away. That would require it to potentially be more like a spider mine where the damage is only a potential that can be picked off in certain situations.
So this is probably not an optimal ability, but it should be enough to get an impression on how it works as space control (and whatever other aspect the player can conjure)