Accelerate/Decelerate

This Spell is a Rare Spell these type of spell you need to find or unlock from a spell scroll or some other Source(optional rule)

You make a minor change to the way time interacts with a single creature or object within range. Until the end of your next turn, the target’s speed is reduced or increased by 15 feet. Likewise, if the creature falls 25 feet or less before the spell ends, it lands on its feet and has resistance to any falling damage it takes.