Arcane Duel

As a wizard starts to form somatic gestures and fire begins to ball together, or a Warlock wickedly grins as eldritch force leaves their focus at an evil speed, you harness the magic within in and Lock up their spell with Arcane Duel.

Placing yourself and your foe into a Dangerous Duel of power...

When a Ranged attack or Area Spell/Cantrip is about to be cast, you can spend 1 Reaction to cast Arcane Duel immediately expending a spell lot of equal level to the Spell being cast.

if the spell is a Higher Level than you posses, Expend a Spell lot from highest to lowest until the spell slots Expended matches the Spell

E.G 1    (DM)Fireball level 5 cast- (Player) 1Reaction and expend spell slot to cast Arcane Duel... (Players highest level for fireball is 3) Expend 2 more spell slots highest slots expended first

E.G 2    (DM)Fireball level 7 cast- (Player) 1Reaction and expend spell slot to cast Arcane Duel... (Players highest level for fireball is 3) Expend 4 more spell slots highest slots expended first

Now your magics are Intwined and a test of Constitution ensues... 

R1 - In the same turn as Arcane Duel is Cast,  At the end of the round all Characters using Arcane Duel roll Constitution saving throws. if a caster involved does not have Arcane Duel they roll at Disadvantage The player with the lowest role takes 5pts of damage (type from spell) as the spells are Locked to each other growing with pulsing ferocity. A constitution save is needed for the damaged caster,to Concentrate.  On a Fail the spell goes off and is targeted and centered at the failed caster and Ends the Arcane Dual.

R2- At the end Round 2 all Characters using Arcane Duel roll Constitution saving throws. if a caster involved does not have Arcane Duel they roll at Disadvantage. The player with the lowest role takes 8pts of damage (type from spell) as the spells are Locked to each other growing with pulsing ferocity.. A constitution save is needed for the damaged caster to Concentrate on a Fail the spell is targeted and centered at the failed caster and Ends the Arcane Dual.

R3- At the end Round 3 all Characters using Arcane Duel roll Constitution saving throws. if a caster involved does not have Arcane Duel they roll at Disadvantage. The player with the lowest role takes...

Rolled Damage from Initial Spell +10pts of damage (type from spell) 

The full brunt of the spell takes effect on the losing Caster....

At Higher Levels

level8.   Rolled Damage from Initial Spell R1  +10pts, R2  +12pts, R3 +15pts of damage (type from spell) . The Losing Caster also suffers 1 Level of Exhaustion

Level 12.Rolled Damage from Initial Spell R1  +15pts, R2  +117pts, R3 +20pts of damage (type from spell) . The Losing Caster also suffers 1 Level of Exhaustion, And is Knocked Prone

Level15. Rolled Damage from Initial Spell R1  +15pts, R2  +17pts, R3 +20pts +10pts of damage (type from spell) . The Losing Caster also suffers 2 Levels of Exhaustion, And is Knocked Prone, Any Critical 20 during Con saving throws per round, results in loser taking double damage

Level 20. Rolled Damage from Initial Spell R1  +20pts, R2  +25pts, R3 +30pts of damage (type from spell) . The Losing Caster also suffers 2 Levels of Exhaustion, And is Knocked Prone, Any Critical 20 during Con saving throws per round, results in loser taking double damage, Advantage on Con Saves in Duel, take half Damage on Losing