Recently, I was taking a look through the Wizard spell list, and the Wall of Sand spell sparked my interest:
You conjure up a wall of swirling sand on the ground at a point you can see within range. You can make the wall up to 30 feet long, 10 feet high, and 10 feet thick, and it vanishes when the spell ends. It blocks line of sight but not movement. A creature is blinded while in the wall’s space and must spend 3 feet of movement for every 1 foot it moves there.
Blinded is a relatively powerful condition, and applying it without a save seems very strong. However, the Wall of Sand spell also blocks line of sight. If a creature also becomes heavily obscured by the wall, it would negate many of the benefits of applying the blinded condition.
It seems like a caster could circumvent the issue by placing the wall to partially intersect a creature. For example, a Wall of Sand could include half of the squares occupied by a large creature. Because at least one of the creature's squares is within the wall, the creature is within the wall, and therefore blinded. However, at least one of the creature's squares is not within the wall, so the creature is not heavily obscured.
Would this strategy work under the variant rule "Playing on a Grid"? Could this strategy also be applied to Medium-sized creatures?