If it's random, which I didn't realise, make the outcomes public and validated.
Something like a % table where it's likely to go conditionally good or bad and a small chance for catastrophic events.
Then, make agreement among the Devs what limits a portal event would have. Reduction of a walls strength instead of removal altogether, or moving characters or a single living from the dead. Make that fairly absolute, with some flex to reward exceptional RP or circumstances.
Those level five walls must have cost a fortune on their own let alone the other actions.
