Aster's magical frog tongues

Green and brown frog's and toads covered in floating specks of red magic, fill a 20-foot-radius sphere centered on a point you choose within range. The sphere spreads around corners. The sphere remains for the duration. The sphere's area is difficult terrain.

When the area appears, each creature in it must make a Constitution saving throw. A creature takes 2d10 bludgeoning damage on a failed save, or half as much damage on a successful one. The target must also make a Strength saving throw, dc 16, or the target is grappled with long magical frog tongues. 

At Higher Levels. When you cast this spell using a spell slot of 6th level or higher, the damage increases by 1d10 for each slot level above 3th.