Help with pricing odd disadvantage

[Flyndaran]

I'm thinking of an environment causing a mutating effect on those that stay in it for too long.

Roll Ht every day in it. Failure margin adds that many points in disadvantages of a "magical" nature. Success does nothing. Critical success adds 5 points in advantages. Three critical successes in a row acclimatizes the character to the area and no longer needs to roll.

Going back to a safe area causes the points, good and bad, to fade down to a minimum of 10% the previous total.

I can't just call it a feature of the world, as there are differing levels of mana-radiation, none, low, high, and very high.

Those from lower to higher suffer quicker, once per day, once per hour, and once per minute. Those from higher to lower suffer in more mundane ways like loss of magical abilities and a vanilla damage per unit of time.

Any help would be most appreciated, thank you.