Vanlig's Instant Lapse

Choose a creature within range. When that creature initiates an attack with a weapon, you immediately cause the earth beneath it to momentarily turn fluid. The target must succeed on a Dexterity saving throw or lose its balance, resulting in a sloppy attack, made with disadvantage. On a successful save the attack is performed normally. The change is not strong enough to make the creature fall prone or otherwise influence its movement. At the end of the attack, the earth beneath the creature returns to normal.