Diabolic Studies

Starting when you choose this arcane tradition at 2nd level, you can speak, read, and write Infernal.

Additionally, whenever you make an Intelligence (History, Religion) check related to devils or the Nine Hells, you are considered proficient in the History or Religion skill and add double your proficiency bonus to the check, instead of your normal proficiency bonus.

Fiendish Contract

At 2nd-level, you add the find familiar spell to your spell book if its not all ready there.

When you cast the spell, you can choose one of the normal forms for your familiar or the form of an imp.

Additionally, you can use your action on your turn to command your familiar to make one attack with its reaction.

Dark Secrets

When you choose this tradition at 2nd-level, you enter a fiendish contract that has granted you a fragment of forbidden arcane knowledge. You gain one invocation of your choice from the Warlock's Eldritch Invocations list. The invocation you choose must have no prerequisites. If the invocation requires a warlock spell slot, you can use a wizard spell slot instead.

Additionally, when you gain a level in this class, you can choose one of the invocations you know and replace it with another invocation

You gain a second invocation of your choice that meets the above requirements at 10th level.

Greater Fiendish Contract

At 6th level, when you cast the find familiar spell, your familiar can take on a more powerful form.

Your wizard level determines which devils your familar can be, as shown in the Fiendish Familiar table. At 6th level, for example, your familiar can be any devil that has a challenge rating of 2 or lower.