Bond of Friendship

You can forge an empowering bond among people who are friendly with each other. 

As an action, you choose a number of willing creatures within 30 feet of you (this can include yourself) equal to your proficiency bonus. You create a magical bond among them for 10 minutes. While any bonded creature is within 30 feet of another, the creature rolls a d4 and adds the number rolled to the first attack roll, ability check, or a saving throw it makes each round. Each creature can add the d4 no more than once per round. You can use this feature once per long rest.