Bubble Goop

You breathe out a bubble that floats quickly toward one creature within range.  If the creature fails a Dexterity saving throw, the bubble bursts over it and covers it with goo.  Creatures covered with goo suffer a -2 penalty to attack rolls and Dexterity checks, and their speed is reduced by 10 feet.  In addition, creatures covered in bubble goop can't cast spells with somatic components.

The bubble goop remains until an affected creature or an adjacent ally uses an action to scrape it off and the affected creature makes a successful Dexterity check.

Enhancement:  For each spell slot used higher than 4th level, you can create one additional bubble.  Each bubble can be targeted against a different creature.