Dense

You attempt to alter the weight of a moving Medium or smaller creature in a short burst. The target must make a Constitution saving throw. On a failure, the target's speed is 0. On a success, the target's speed is halved. The spell ends until the start of the creature's turn

An airborne creature affected by the spell will have difficulty carrying itself but does not fall to the ground. It still suffers the same movement penalty.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the spell target size increases by one for each slot level above 1st.