[quote=@Zetsuko]
[@Zelosse] it's an area of effect pulse, at least they can't conjure more right?
[/quote]

Do you drain mana or do you suppress magic.
Demons are summoned, their masters maintain the link to the material plane. 
I believe there was two ways to summon demons from an old book I read.
One was a sacrificial offering. These are blooded demons that need to be beaten or banished.
The others are brought in from a gateway, created by a summoner. This requires the master to have the magic available to keep the demons linked to our world.

Take away the mana, take away the summons.
The ritual invoked need to be out down the old fashioned way.

With that in mind, lets see what you can really do ;)
"level the playing field"