So, there is this entity in my story, Slenderman, who's ultimate technique is the Blackout.
Blackout causes electronic devices and light-based communication to fail within a 5 km radius of a chosen point. In layman terms, it makes everything foggy (that fog are the machines themselves), pitch black and also gradually deteriorates electric components like transistors and batteries. The thing is, Slendy can't use this insanely powerful ability for anything else.
It's strange. The micro machines (50-100 micrometers), he uses, can do different things when ordered to, yet the constituent bots of Blackout can't do anything besides chewing telephone cables and being impenetrable to a wide spectrum of light.
How can I explain the Blackout bots' inability to do anything besides what's in the ability's description, in particular, its inability to be wielded offensively against organic lifeforms?