Burden of Pain

When an ally you can see within range suffers damage, you can use your reaction to call your god's help and reduce the damage taken by this creature. You take 1d4 necrotic damage, which can’t be reduced in any way, and the damage that the creature of your choice suffers is reduced by a number equal to the necrotic damage you take.

You have to take your reaction before you know the number of damage your ally will suffer and you cannot take more damage than your ally.

The spell's damage increases by 1d4 when you reach 5th level (2d4), 11th level (3d4), and 17th level (4d4).