An ability with this limitation GURPS Horror pg 22 defines this as -20% for 1 point of Corruption for reduced cost, if applied to an advantage.
Corruption as a disadvantage is worth -1% per 10, so -20% worth of "Temporary Disadvantage: Corruption -20%" would mean you temporarily accrue 200 points. This would mean:
- "Saintly, divine, or otherwise anti-Corrupt beings" would react at -8 (-1 per 25)
- a weekly will roll at a -20 penalty to prevent the 200 corruption from converting into -8 character points
148 note "Once someone has 125+ points of Corruption, the GM may convert it into negative character points regardless of the Will roll." so because of that, the safest would be "Temporary Disadvantage: 120 Corruption -12%" this would mean reactions at -4 (it's per FULL 25) and will rolls at -12 (unclear if this qualifies as a 'resistance' roll or not) to prevent 120 points converting into -4 character points