Arena Axe Beak

Stampede. These birds have been trained to fear an instigating predator.  The trainers make the birds irrationally afraid of this foe and use the predator to work the birds up into quite a frenzy.  When the birds are released into the arena they will stampede as a very large single group, trampling all creatures medium size or smaller in their path. 

This DM should treat their path as a 5' foot wide by 50' foot long line, then add 1 more foot to the width for every bird involved, and 10' feet to the length for every four birds involved (starting at 6' feet wide on reaching 2 birds and 60' feet long on reaching 4 birds.)

Every creature of appropriate size in this path must make a DEX saving throw (DC 11 (+1 per every 4 birds)) or be trampled by the birds.  Getting caught in a axe beak stampede will take (1d6) bludgeoning damage (+1 point per every 2 birds involved). 

For example a stampede of a dozen axe beaks will cause a stampede 11' feet wide by 80' feet long, DC14, causing 1d6+6 hit points of bludgeoning damage).  All those that make their saving throws will take only half damage.  Large creature will automatically only take half damage and will be able to save for no damage.  Creature larger than this will not be harmed by being caught in a axe beak stampede.  The area where the birds charge through will be difficult terrain until the end of the next turn.

Beak. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d8 + 2) slashing damage.