Wait for Menara Voidrender to complete the Orb of Dar'Orahil and then speak to her again.
I will get started immediately on crafting your orb and infusing your new demon into it. When done, you will have the choice of having it in the form of a staff or orb. I always felt it was important to cater to a warlock's chosen weapon... I see no reason not to continue that practice.