Disrupt Spell

Disrupting a spell is easier than undoing it, but has an element of uncertainty. 

You randomly alter a spell cast by a creature you can see in range. Roll a d8 and apply the effect from the following table. If the target spell was cast using a higher level spell slot than this spell, roll twice and take the higher result. The changes to the spell last for that spell's duration. 

1: Rebound. The spell's target becomes the spell’s caster, or if there is no target any areas of effect are centered on the caster. If the spell’s target was already its caster, the spell fails. 

2-4: Weaken. Creatures have advantage on saving throws made to resist the effects of the spell, and any attack rolls made as part of the spell are made with disadvantage. 

5-7: Shrink. The dimensions of any area of effect is reduced by half, or if there is no area of effect the range of the spell is reduced by half, potentially causing it to fail. 

8: Amplify. Creatures have disadvantage on saving throws made to resist the effects of the spell, and any attack rolls made as part of the spell are made with advantage.