Chronological Punishment

You gather the power of all slashes made from enemies made 6 seconds prior. As an action, you can choose up to 5 creatures (friend or foe and including you) within 60ft from you and calculate the collective  amount of attacks made by them during the PREVIOUS turn. All creatures chosen must make an intelligence saving throw. If a target fails, they are susceptible to taking all or a portion of the damage chosen by the caster. If they succeed, they aren't susceptible to any damage unless they willingly decide to fail the save in order to potentially save their teammates who have failed. The damage totals to (amount of attacks collectively) x d10 + (amount of attacks collectively). The caster can split the damage amongst the creatures that have failed  to hi will. This said, he can make one person take all damage as much as he can make some take partial damage or even make no one take damage if the spell backfires.