Whenever another creature you control dies, put a +1/+1 counter on Unruly Mob.
"Who says werewolves are the only ones who can hunt as a pack?" —Kolman, elder of Gatstaf
Official Rulings for Unruly Mob
9/22/2011 : If Unruly Mob and another creature you control die simultaneously (perhaps because they were both attacking or blocking), Unruly Mob will die before its triggered ability resolves. It can't be saved by the +1/+1 counter that would have been put on it.