Pures and other accounts with 1 defence and prayer can't do quests such as restless ghost and dragon slayer because if they do it destroys the cause for that account, they go up a prayer or defence. Because they can't do these quests they can't get the benfeits of the quest, such as: being able to train on crandor, not being able to complete the lumbridge achievement diary or upgrading your gravestone and more. I sugest at the end of the quest, when the rewards certificate saying you have completed the quest comes up. By the experience points e.g. 3000 magic exp, it says yes or no. Yes meaning: You want the exp and no meaning: you don't want it. (I'm F2P so i don't know anything about the P2P quests)