Artillery starts out looking like an ordinary military base, but during gameplay, a storm kicks up. Lightning begins to flash on the horizon and eventually a tornado develops and sweeps near the play space. Dust and debris are kicked up, making it difficult to see, and the buffeting winds can mask your approach.
To get the Electric Cleaver, play on Horde and buy any base and start the wave. Before you can begin the process for the Cleaver, you need to be in a "savage" wave. Indicators of this are wild Tickers, and of course Savage Locust. If the wave contains Lambent, Wretches, Shriekers etc., then you don't have the right set currently. Keep playing or die and restart the match. The reason you need a savage wave is because you must obtain a Cleaver before you can progress. Next, find a Butcher or Savage Theron. Kill it and take its Cleaver. Head towards the Headquarters spawn. Bring the Cleaver with you; you will need it soon. Wait for the storm to pick up (a siren will sound when it's beginning) then stand on top of the "High Voltage" sign that is on the ground in the wide open with the Cleaver in your hand. Lightning will strike you, charging the cleaver. You now have an Electric Cleaver!