Disrupt

*which you take when you see a creature within 60 feet casting a spell

You attempt to disrupt a creature in the process of casting a spell. The target must make a saving throw with their spellcasting attribute, or Constitution if the spell is not tied to a spellcasting attribute. On a failure, the spell they're casting is weakened in all of the following ways that apply at any point during the spell's duration:

• the caster has disadvantage on attack rolls made for the spell
• all creatures affected by the spell have advantage on saving throws made against the spell
• saving throws made to maintain concentration on the spell have disadvantage

If the triggering spell was cast using a spell slot of a higher level than the slot you used to cast this spell, the caster adds a bonus to their saving throw equal to the number of slot levels by which their spell exceeds yours.