Thunder of Hooves deals X damage to each creature without flying and each player, where X is the number of Beasts on the battlefield.
Illustrated by Jim Nelson · Onslaught · #242
There are no rulings for Thunder of Hooves.
Chain Reaction deals X damage to each creature, where X is the number of creatures on the battlefield.
Sacrifice a creature. Rupture deals damage equal to that creature's power to each creature without flying and each player.
Gates Ablaze deals X damage to each creature, where X is the number of Gates you control.
Flamebreak deals 3 damage to each creature without flying and each player. Creatures dealt damage this way can't be regenerated this turn.
Calamitous Cave-In deals X damage to each creature and each planeswalker, where X is the number of Caves you control plus the number of Cave cards in your graveyard.
Echo (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)
When this creature enters or leaves the battlefield, it deals 1 damage to each creature without flying.