You've seen warlocks in WoW summon their felhounds 1 at a time, but what happens when you have hundreds of them?

*Edit*
Please download the video for better quality. The youtube stream quality is very bad.
I will now reveal how this was done to keep it a secret, but I assure you that this was done on a live server, not a private server. The felhounds were not the same type of felhounds that warlocks can summon from soul shards, which was why I was able to produce these on a paladin and a druid..