Vermintide

You conjure a huge swarm of rats in any location you can see within range.  The swarm dies when it drops to 0 hitpoints.  The swarm is friendly to you  and your companions.  Roll initiative for the swarm, which has its own turns.  It obeys any verbal commands that you issue to it.  If you don't issue it any commands, the swarm will spend its turn seeking out the nearest source of food.  If a swarm is alive after 8 hours, you will lose control over it and the swarm will disband into an appropriate number of tiny rats.  You can recast the spell before it expires to regain control over swarm again.  

The swarm statistics have AC11, 216 hitpoints.