I'm running an high level campaign where two players brought to the table two very powerful and costly intelligent items, which they filled with every kind of spell they could need. They also gave them a special purpose to be able to get the best stuff around. My question is, by RAW, the special purpose have to chosen among the ones provided in the column (for example: defeat this kind of creatures) or can be chosen by the player? Because I think that the purpose of "keeping Player X alive" is a bit too cheesy and almost cheaty.