Just a suggestion, maybe Bonus Damage can be added if an opponent is pushed against the wall by items with knock back.

Example 1

Opponent is 1 square away from the wall. You hit it with something which grants 2 squares of knock back. Opponent takes extra damage from 1 square of knock back against the wall.


Example 2


Opponent is beside the wall. You hit it with something which grants 2 squares of knock back. Opponent takes extra damage from 2 squares of knock back against the wall.


Bonus damage should be balanced carefully.

I agree with you if you mean that when opponents have their backs against the wall they should be more vulnerable and take more damage. This will make people quit camping in a corner.