It seems to me that the purge disease spell given by the Questy Object doesn't cost the 25 mana, no matter whether it fails or
succeeds.

<385/561m 677<677> 12163tnl 5 AM civilized>
c 'purge dis
A questy object grows warm in your paw.
You lost your concentration.

<385/561m 677<677> 12163tnl 5 AM civilized>
c 'purge dis
A questy object grows warm in your paw.
You aren't ill.

<385/561m 677<677> 12163tnl 5 AM civilized>


Tried it a few times later, too, and it didn't cost any mana then
either.