Terrain of Juiblex

After a chance encounter, the Lord of Ooze has granted you a small boon to help you change the world in his image. 

You create a single 5 by 5 foot space on the ground of thick ooze directly from the pits. The space is covered in an inch of ooze of your choice of color. Any creature that starts their turn in this space or attempts to cross on foot must make a DC 15 dex save or will have its Speed reduced to 0. If a creature takes the dash action and fails the save, it instead falls prone in the next space in the direction it was moving. 

A prone creature in a terrain space must succeed a DC  15 strength check or take 1d4 acid damage. If they succeed, they stand up on the space but still have a move speed of 0. 

 When you use this spell at 4th level or higher, you can create an additional space per level.