FATE Core - Corruption

I'm in the process of making a game for one of my groups, the pitch is that a shower of meteorites have left a deposit of "starstuff" which when used/comes into contact with people grants them powers and also begins to corrupt them, eventually turning them into mindless creatures.

For the corruption I've so far got an aspect and a skill.

Aspect - Corrupting Power from Beyond the Stars

Any character that has used the “starstuff” may invoke this aspect for a +2 bonus or a re-roll for free, but a tally of the uses will be taken which will be used to calculate the skill level of Corruption for that character.  Any character that can invoke this aspect for free may instead pay a fate point to avoid the increase in corruption.

Skill - Corruption

This skill is used by the GM alone, it's rating begins at mediocre (+0) when a character first uses the "starstuff." From that point on a tally of free invokes from the above aspect is taken, when the tally becomes greater than the current rating of the skill then the skills rating is increased by one and the tally resets to zero.

The GM can use the skill to create advantages like Drawn to the Dark Side (a situational aspect that can be removed with a Will overcome action) or attack the characters mental stress track (I'll be wicked and "kick them when they are down" in an attempt to get a consequence) both actions are resisted by the characters Will.