Undo Greater Harm

You reverse time around a wound as it forms, attempting to undo what has been done.

Choose a creature you can see within 30 ft that was recently attacked, after the damage has been calculated but before they've been harmed. As a reaction, you can choose to halve the damage. 

At Higher Levels: When you cast this spell using higher spell slots, you can choose additional ways to undo harm per spell level:

• 3rd: Choose additional creatures to undo harm from the same attack (such as an Area of Effect ability). 
• 5th: Any resulting effects (such as paralysis, poison, becoming grappled, etc)
• 7th: Undo all the damage on up to one attack
• 9th: Undo all damage of all attacks and effects against creatures of your choosing until the start of your next turn 

As in, at 7th level, you can choose to undo all damage from one attack and resulting effects for one attack on up to 4 creatures.