Swarm of Geese

All geese from the flock that are in range immediately swarm the individual who killed one of their own with a thirst for vengeance. 

The swarm does 1d4 damage per round if there are less than 10 geese, 1d6 damage per round if there are 11-15 geese, 1d8 damage per round if there are 16-20 geese, 1d10 damage per round if there are 20-30 geese, and 1d12 damage per round if there are more than 30 geese. If the target is submerged in water or flying, the damage is reduced by half.

The swarm continues until the target is unconscious (not dead) or Wilheim uses an action to calm down the swarm. The swarm also ends if the target goes inside an enclosed building.

While effected by the swarm, the target is limited to half its movement speed and one action per round (no additional actions, bonus actions or reactions).

Any creature that is not the target that is within the 10 ft. sphere of the swarm suffers one round of damage and is pushed outside the spell range. Attempting to enter the swarm from the outside causes the same damage and success on a DC12 Strength check for less than 10 geese, a DC14 Strength check for 11-15 geese, a DC16 Strength check for 16-20 geese, a DC18 Strength check for 20-30 geese, and a DC20 Strength check for more than 30 geese.