Pipes of the Sewers

You must be proficient with wind instruments to use these pipes. The pipes have 3 charges and regain 1d3 expended charges at dawn. 

You can use an action to expend 1 to 3 charges and play the pipes, summoning a swarm of rats for each expended charge. Summoned swarms are not under anyone’s control and appear by the shortest available route, and if there are not enough rats within a half mile (at the Narrator’s discretion) for this to take effect the expended charges are wasted and no swarm is summoned.

While you are using an action to play the pipes, you can make a Charisma check contested by the Wisdom check of a swarm of rats within 30 feet. On a failure, the swarm acts normally and is immune to the pipes for 24 hours. On a success, the swarm becomes friendly to you and your allies until you stop playing the pipes, following your commands. If not given any commands a friendly swarm defends itself but otherwise takes no actions. Any friendly swarm that begins its turn unable to hear music from the pipes breaks your control, behaving as normal and immune to the effects of the pipes for 24 hours.