Backfire

Also known as "Teg's No, You", You attempt to redirect the energy of a spell in progress. If a creature is casting a spell of 4th level or lower, its spell's energy is redirected from its original target. If it is casting a spell of 5th level or higher, make an ability check using your spellcasting ability. The DC equals 10 + the spell's level. On a success, the spell can be redirected. 

Redirection to a new target uses the remaining distance of the spell. Such as if the spell "Fireball" is backfired and the original caster casted the spell 30 feet to its target if the spell is successfully redirected you can use the remaining 120 feet of the spell's range to determine the spell's new target. If the spell does not have any distance left the spell is redirected to a 5 ft space next to the target.

Spell damage and DC saving throws are determined from the original caster. 

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the spell can be redirected if its level is less than or equal to the level of the spell slot you used.