The GM can also lay compels against the player relating to the nature of the IoP and the oaths, requirements, etc. that come with the wielding of that IoP. For example, Michael is often limited regarding the use to which he can put the Sword. I see a number of places in the series where the player of Michael might have wanted to slay a coin-bearer (for example) outright, but the GM stepped in, handed the player a Fate point, and said "Don't you think it would be better to try your absolute hardest to save the poor mortal soul locked within that monster's body?"