by MDJD
Quoted directly from the rule book: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 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 a 3 die attack (Armor reduces this damage normally). This special attack cannot be avoided. Note the walls around the outside of the arena all have the Passage Blocked trait. Note that Flying creatures ignore walls. Some creatures and all conjurations have the Unmovable trait. They cannot be Pushed and ignore all Push effects.
Please especially see the highlighted part. Push is not random if source and object of the push are in the same zone.