Chrono-blast

A ripple of energy emits from your palms. If the target falls prone as a result of this attack, it does so in slow motion.

The target must succeed on a Constitution Saving Throw. If the target fails, you may spend 1 bonus action to either have the target fall prone or have it's speed reduced by half on it's next turn. 

Starting at level 5, whenever the target fails it's Constitution Saving Throw, you may spend 1 bonus action to have both effects. 

The damage is increased by 1d6 at 5th level (2d6), 10th level (3d6), and 15th level (4d6)