Soul Drain Refresh Cost

[atomzero]

There is a player in a game I'm in who wants to put this ability on on a sword:

Soul Drain
The sword thirsts for energy, readily exchanging power for spirit. The user may spend a Mental Health Box per Level of Increase to boost the Damage of the sword and deal Spirit Damage.

What would be an appropriate refresh cost?

[Tedronai]

A few minor tweaks:
'Mental Stress', not 'Mental Health'
There is no such thing as 'Spirit Damage'.  If I'm interpreting your intent correctly, the closest would again likely be 'Mental Stress'.

I would advise against charging stress boxes for this power.  That would become prohibitively expensive very quickly.  Instead, charge an amount of stress equal to the bonus, a surcharge (of at least 2) if they want to convert the attack to mental stress, and a cap on the total cost applied to any given attack equal to the length of the user's mental stress track.

Contingent on those changes, and an explicit understanding that the power might be subject to revisions if it proves to be unbalancing or otherwise problematic, I would charge one refresh for this power.

[atomzero]

Thank you for your help.

[Sanctaphrax]

I'd assign a higher cost, personally. Mental stress totally ignores Toughness and lets you exploit a potentially-smaller stress track.

With this Power, handing out weapon 6 mental attacks is easy. And there's essentially nothing that can take such an attack without consequences.

PS: This seems remarkably similar to the Supernatural Martial Arts Power I've been working on over on the Custom Powers Master List thread.

Perhaps I should add a mental-stress-inflicting option to that Power...