What type of toughness powers does he want? If he only wants inhuman level powers, then a [+0] catch will work just fine. If you want to grant the player some refresh back, you could attach it to human form (involuntary change), which will then be sort of like the catch. The human form trigger would then be anything that would oppose the spirits agenda.
If he is going for more than inhuman, I would require him to take up a catch that can be met by other people, simply because he will become nigh invincible otherwise.