Classifying the tutoring from demonic origins
In Magic the Gathering, tutoring and drawing cards are an analogy for learning. In the color black specifically, they do this through the sacrifice of their health in exchange for knowledge.
On one end of the spectrum is Dark Confidant, who draws you a card and then you lose life based on the mana cost of the card. If it's a land card you lose nothing, but if it's a Blightsteel Colossus you might lose 12 life. On the other side of that spectrum is Griselbrand, who lets you draw 7 cards for 7 life. You can't cheat his system by paying less life for cards, you have to pay 7 and you have to draw 7. If each card drawn is equivalent to 1 life then the 0 cost land might have hurt you a bit, but the 12 mana colossus also hurts you for 1 all the same. In the middle of this is Villis, Broker of Blood who can let you draw cards per life lost. You can go to him directly for a blood offering of 2 life for 2 cards or he'll let you draw as you lose your life naturally.
Obviously, in game there are cost implications like how Dark Confidant is 2 cost and also a human while Griselbrand costs 8 and is also an archdemon, but the implication is that Griselbrand is better at the contract between you and him, where he will do it more efficiently at possibly even less risk to yourself. Meanwhile, Villis seems more conniving, he's fine with you getting something at even a discount, but he's waiting for all of your life to go so he can collect.
On the other hand, the art that depicts Demonic Tutor, Diabolic Tutor, and Grim Tutor. Grim Tutor implies that you attempted to do it all on your own through a sacrifice of blood which is why it costs 3 life. Demonic Tutor shows that you are speaking directly to the demon itself which is why it's free while Diabolic Tutor implies that you are talking not to a demon but to a denizen of the underworld.