Balagarn's Iron Horn

You create a deep, resonant vibration that can shake creatures off their feet as if they were being tripped. Make a single Strength check as if your Strength were 20. Creatures in the area make individual opposed Dexterity or Strength checks against your roll. Those who fail are tripped and fall Prone. Those who succeed are unaffected, but cannot make a trip attack against you in response to this spell. Unlike a regular trip attack, you may trip any creature touching the ground, regardless of size.