Cataclysm

When casting this spell, you scatter the gemstone dust to the winds, and the affected area becomes shrouded in darkness as hundreds of meteors descend from the heavens. Roll all dice present on the table with the exception of any percentile dice and add up the total. Roll a secondary percentile die, the results of which will become the percent of the total dice rolled in bludgeoning damage*. All creatures in the 60 ft cube you choose must succeed on a dex saving throw. You take full damage on a successful save, half damage on an unsuccessful one. 

*For example, if you rolled 100 damage on all dice on the table, you would then roll your percentage dice. If you were, for example, to roll a 50 on your percentile die, then you would take 50% of 100 damage you rolled previously which would be 50 bludgeoning damage. If affected creatures succeed on a dex save, they would take half damage, so instead of 50 bludgeoning, they would take 25.