Cillian's Bardic Epiphany

You inspire your party with an unparalleled performance. Choose a number of creatures within range upto your Charisma modifier that have been granted a Bardic Inspiration die by the bard class feature (you can choose yourself). Until the end of your next turn, the die is doubled (2d6, 2d8, 2d10 and so on...).  Once you have cast this spell, it has a 50% chance of failure until your next long rest.