Taken from the Codex.
Push
Push is an effect caused by some spells and attacks that moves the target
into an adjacent zone. Unless the effect says otherwise, the Pushed creature
must move one zone away in the opposite direction from the source of the
Push. If there is a choice of direction (such as pushing a creature diagonally
opposite, or if the source of the Push is in the same zone as the target), the
source of the Push chooses the direction.Some spells may Push in a random direction. To determine the direction,
choose one side of the board to be “North” and roll the Effect Die: a 1-3
Pushes the creature North, 4-6 = East, 7-9 = South and 10-12 = West.
A creature may be Pushed through a wall, but only if the wall does not have
the Passage Blocked trait. The Pushed creature suffers any attack from the
wall if the wall has the Passage Attacks trait. If a creature is Pushed into
a wall with the Passage Blocked trait, it is Bashed against the wall and
suffers an Unavoidable attack of 3 attack dice. Note the walls around the
outside of the arena all have the Passage Blocked trait. Note that Flying
creatures ignore walls, except for the ones around the outside of the arena.
Some creatures and all conjurations have the
Unmovable trait. They cannot be Pushed and ignore
all Push effects.