Arcane Swiftness

Benefits: Twice a day, after casting a spell using your action you can use your bonus action to cast another spell which has to be the same or lower level of the first spell. You can use this ability once more per day at level 6 and again at level 12.

Disadvantages: Each time you use this ability roll a Saving Throw on your spell casting ability CD 15. On a fail you get disadvantage on the attack roll of the second spell or the target gets advantage to his saving throw. If none of those can be applied the time that the spell remains active or the eventual effects are divided by two.